There is a converse to internet searches--information on the internet may or may not reflect what people are seeing in stores. Just as in the old catalog days, just because it is listed, does not mean it is really available nor is it very popular. Regarding the PX4 Storm, I haven't seen the Inox slide version in the various gun stores around. I am sure that perhaps Davidson's or some of the other distributors may list it in the books--but is may be special order, allocated, limited runs, etc. so in effect is "unavailable". Marlin in particular may list all of those in their online catalog but exactly how many are shipping? You can find elsewhere on the THR, some posters' frustrations that it is listed but no one has them.
In my case, I have been doing an AR build recently and looked through an number of suppliers barrels to do so, I found anecdotally fewer stainless steel barrels that were available for the build that was interested in compared with a few years ago, I did find many more nitrocarburized (melonite etc.), fewer chrome lined, and the regular parkerized chrome moly being sold as the cheapest but generally available everywhere. Would that reflect everyone's experience, possibly not. Does their experience reflect mine, probably not. Would the internet answer this question, maybe, maybe not. Probably, it would be the same for other types of firearms as well.
During the catalog years, it was and is still common to check these for firearm history to determine whether a firearm was produced by the mfg (listed in the catalog) and then whether the used gun's modifications occurred at the factory, was a factory special order or overrun from a special lot, or modifications were done by someone else either an amateur or professional gunsmith. I have a pre-model 15 made in the transition year of 1957, it has a 5 inch barrel. Now through Supica, I found out that the serial number matched for a series made specially for the Illinois State Police with just that barrel but mine has no police markings nor any sign that these were obliterated (firearm appears to have its original finish). Thus, I conclude that it was sold as an overrun of that special order to my satisfaction (probably need to get the factory letter one of these days though).
It is possible that the 1957 catalog of S&W listed the 5 inch barrel as an option--don't have one so I don't know. But, if the 5 inch barrel used to be regularly made and it disappeared as a generally available option (this is a hypothetical--S&W collectors count the number of screws and such things and probably know the answer). I might have asked in 1957 in a letter to Gun Digest or G&A, "Where have all of the 5 inch barrels gone?"
Generally speaking, people post on THR because they want knowledge, want to talk about something they've observed, or are just being social. A good rule of thumb is pass by threads that you are not interested in or in your mind think have already been answered. I have no interest in caliber wars--whether you carry a 9mm, .40, .357, etc. I don't care. I might comment on my personal use of a caliber but try to not believe nor imply that reflects reality for everyone. Likewise, my interest and knowledge in extreme long range shooting is low--but if I did decide to take it up, I would probably start by making what some would term stupid or ignorant questions on the THR.
Live and let live, love thy fellow THR poster as thy does oneself, and keep your words sweet as you might have to eat them later, are good maxims that apply here. Nuff said as I always run long on posts.