I learned something many years ago.
If I check to confirm the magazine I'm inserting into the pistol is full before I insert it into the pistol, and after I release the slide to run forward and go into battery there's suddenly one less round in the magazine when I remove it to top it off (or just confirm the top round was loaded/chambered), it's more than likely in the chamber.
Where did the now-missing round go, if not into the chamber?
Also, unless I'm replacing a partially spent magazine with a fresh one, where I want to keep the chambered round
chambered and ready-to-fire, I really prefer to load the chamber from the condition of the slide being locked back. Easier to insert and fully seat the magazine. Only have to release the slide, meaning not having to
fully retract and release it (and it's an even easier manipulation if you release the slide via depressing the slide stop, since I spent many, many years doing it that way using 1911's and 3rd gen S&W's). Also, after the mag is seated, it also only requires the dominant hand to get the weapon back into action. You never know if sometimes that support hand may become busy with some other critical task of the moment.
Now, as long as someone who has been trained to do a "press check (or has adopted the habit over the years) doesn't set themselves up for a problem that could result in an injury, or cause an ammo/magazine condition which might result in a feeding stoppage the next round up (I've seen that happen), I don't really care one way or the other how other folks feel about press checks. Safety and controllable manipulation loading the weapon so it's ready is the goal.
I do, however, find the loaded chamber visual inspection port, which allows you to see the case rim or web of a chambered round, is a handy feature.
FWIW, the caution against covering the ejection port to try and catch an ejected live round - versus just letting it be ejected to fall free - is one that ought not be ignored. In one of my armorer recerts we were shown a picture of a cop shooter who had suffered severe injury of his hand/fingers when a live round he was trying to eject and catch
did shift so the ejector hit and ignited the round's primer. Nasty.
