You clearly miss the point.
When you define something by the legal terms used for a regulated item you remove half of the argument that it is not a regulated item if the need were to arise.
Silencer is a legal term under federal law, so it means something quite specific in reference to the law. It is an NFA firearm in the United States. Many noise reduction products that reduce the report of machinery and devices which are not firearms are not 'silencers' under federal law.
You you cannot just call an item that is regulated by definition of what it does another name and use it, as you mention.
However when a specific item is regulated by name your use of that name with a legally defined federal definition to refer to another similar but unregulated item is detrimental to you both immediately and later if it was in court.
Sometimes it matters and sometimes it does not.
And yes many items are legal or illegal based on the term adopted for them.
Some flash suppressors are identical to some muzzle breaks, (and some are quite separate and distinct from each other.) Even though they may be designed to accomplish something slightly different, and so are given a different name.
However flash suppressors are an "assault weapon" feature in places including in the whole country during the expired AWB, and muzzle brakes generally are not.
This means the difference of two identical items legally in some cases can be simply the name given by the manufacturer of the item.
The one that calls their product a muzzle brake is legal while the one that calls their product a flash suppressor is restricted more places. The purchaser does not get to rename it, but the manufacturer of the item in this case defines what the item is that they have created, both divert gas in different directions with an attachment on the muzzle for different as well as some overlapping reasons.
Who gets to tell you why that gas is being diverted? The manufacturer of the item, and if they say its to be a muzzle brake and not hide the flash, well they know their product better than anyone else does.
Here I show this example with pictures of a mini-14 attachment as it applies to California law:
Legal muzzle break made by one company:
Illegal felony flash suppressor/hider:
Similarly many guns are banned by name in some places. Yet nearly identical firearms simply renamed are legal. In fact companies and the firearm industry frequently get around bans by name simply by making the firearm with a different name, perhaps changing some minor thing so warrant the name change or different model designation.
The legislation defines the specific firearm by name, and so nearly the same firearm by a different name is not prohibited, the name has a legal definition by law.
In law there is times when the name is very important because it has a legal definition within jurisdictions.
Casually throwing around names that have legal definitions is one of the reasons people have lawyers speak for them, because they can hurt themselves bad just by using the wrong term for something.
By using the terminology of a restricted item you may find yourself limiting your options more when asking someone such as the ATF to give a legal interpretation on whether an item falls into their jurisdiction as a regulated item, or does not.
The ATF has said any device that will reduce the report of a firearm by even one decibel is a silencer. Yet just barrel length the same length of a device reduces the muzzle report by several decibels in many cases. A few more inches of barrel is a decibel or more quieter. Likewise a hollow tube like the fake suppressors sold for some firearms for aesthetic purposes do as well. A little more space for the gas to expand in before it escapes will reduce the decibels if measured with a microphone. They are not intended to be silencers though, so even though they fit the very definition the ATF has previously given of a silencer by reducing the report by at least a decibel, are not silencers.
As the manufacturer of an item the terminology you use is of major importance in some cases. You cannot get away with violating the law by calling something something which it is not, but you can comply with the law by designing something for one purpose or another as a product or within a product that is not regulated the same way.
For example airsoft and bb guns are not held to the laws requiring a red or orange tip many places. While toy guns are.
So if you made such a toy gun without an orange tip without making the distinction that it was a BB gun you could be in violation of many laws. Be charged and fined accordingly.
A toy pea shooter gun designed to shoot green peas would need an orange tip, while an airsoft or bb gun using the same diameter projectile would not need an orange tip.
Your terminology of the item in question would determine the legality of the item.
Some pepper ball guns used in riot control similarly are little different from a paintball gun.
However a pepper ball gun may be restricted by legislation in some places irregardless of what type of ammo is in it, including if it has just regular paint balls in it, just because it is manufactured and sold as some sort of riot control or chemical dispensing device. While a paintball gun may not be.
So the manufacturer's definition of what the item is, even if they both project the same diameter projectile with the same air, can play a huge role in what the item legally is and what restrictions apply.
Pepper spray meant as self-defense from people is illegal or has restrictions some places that the same spray made for bear defense does not. One may be legal or illegal for example in parts of Canada or some states based on what purposes it was manufactured for and the marketing or terminology used by the manufacturer. It may have possession of capacity limits for one type and not another, etc
Even though they are both projecting the same or a similar mixture, the difference can be severe legally. (Now that doesn't make it legal to possess the animal spray for people, or plan for such self-defense, or walk down the street where no bears are in the city, but in other situations it determines just the legality of possession of the product. One product marketed for self-defense against humans is illegal, while the other marketed for bear defense may even be encouraged by the local government. It is not because of what the product does, or what it is per say, but what the manufacturer has defined it as under the law.)
Terminology under the law matters.
