If the factory has, indeed, finally issued a warning about excessive dry firing then as far as I'm concerned, that would be a good thing. When it comes to someone's favorite anything, reality often takes a back seat to both personal preference and popular myth. The way that I see things: Metal is metal; and everything wears out. This is why I own dozens of expensive A-Zoom snap caps.
I dry fire everyday with my carry pistols. You can be certain that I'm not going to risk damage to my own carry piece because, 'Everybody says it's OK to dry fire the heck out of a Glock.' Like I said; 'No matter the manufacturer, metal is still metal; the firing pin's forward momentum is ultimately stopped by the breech face; and anything mechanical will sooner or later wear out.
The shooting range down the road from me swears that they have an original 1st generation G-17 that has more than a million rounds through it. I suspect their estimate is very close to the truth, too. (It's been completely rebuilt; and, the barrel has been replaced, at least, once.) I'm, also, aware of a major midwest state police agency that trades in their service pistols every 5 years (or 40-50,000 rounds) because of their armorers' reports of increased problems with older Glock frames and other components.
So, who really knows? As far as I'm concerned it's better to err on the side of caution. When I dry fire I use snap caps inside of ALL my firearms.
First, Glock's two principal action springs are very easy to replace; so, there's no worry there. (You should keep extras on hand, anyway, right!) Second, you do NOT want to load a fully charged magazine behind a snap cap in a Glock. Many Glocks work best (and most reliably) when they are either hand-charged on an empty chamber, or else from the normal firing impulse created during recoil.
Next, in more than 50 years of handling and using firearms I think it safe to say that I've seen and done it all. This being said: I never, absolutely never, leave a round chambered inside my home. Is there a problem? There really shouldn't be. The fact is that you will respond as you have trained yourself to respond - Period.
The drill for carrying (or storing) a weapon in C-3 is no different than the drill for properly clearing a semiautomatic pistol. You either teach yourself how to, unerringly, do it right the first time and everytime, or you end up with egg on your face after proclaiming something incredibly stupid like; 'I think I'm the only one here (as far as I know) who's professional enough to handle a Glock Fo' Tee!'
Drop the magazine. Clear the chamber. Lower the slide. Do NOT return the magazine to the pistol until you're ready to return the pistol to service. 'C-3 storage' may be considered as a form of, 'service'. The key habit you need to inculcate into your firearms psyche is to never return a loaded magazine to a pistol when the slide is open - UNLESS you anticipate firing the weapon!
Like I said: This is, both, a firearms safety drill as well as an unchanging physical behavior. You do it exactly the same way everytime, or your chances of having a problem somewhere down the line go way up.
Me? I am thoroughly preconditioned to always place my support hand, palm down, over the top of any full-sized pistol's slide and draw it all the way to the rear before allowing it to go forward under its own power. Even if I had a round chambered when moving fast I would, probably, still rack the slide. If you're wondering about how much longer it might take to do this? Typically, about 0.3 second. The disadvantage is that you need to use both hands.
The big advantage is your pistol is going to be a lot safer for your loved ones (and you) to be around. I'll close this out with a subtle fact I've slowly come to learn and appreciate about everyday C-3 carry: Because I know that I'm going to have to use two hands, and that extra 1/3 second has to be there, I tend to be much more alert to the presence of others - their body language, personal behavior, and especially to their hand movement - than many other gunmen who merely carry a sidearm.
As a matter of fact, after 12 years of doing this, I'd recommend C-3 carry to anyone who's daily routine doesn't involve regularly having to draw a weapon. With me it's always more about the safety of my family and friends than it is about being instantly ready to, 'rock 'n roll'.
Most SD gunmen will scrupulously wait, to verify the threat or issue a verbal command and draw, until the problem has advanced to within 7 1/2 yards. Not me! I regularly practice all the way out to 16 1/2 yards; and, I'm ready to begin issuing commands and/or draw at 10 to 12 yards - Which, in a gunfight, has to be a decided advantage!