Not necessarily. It is the continuous shock that exacerbates the problem. The snap cap or live round acts as a shock absorber.
ETA: I’ve actually heard two theories here. The first is that the round/snap cap acts as a shock absorber. The second is that it keeps the stresses where the firing pin was designed to take it. It is my understanding that some designs can’t take the stresses on the firing pin’s “shoulder” i.e. the part of the firing pin that impacts the back of the breech face.
A part that requires an aid as a norm bears an inherent metallurgical or design issue/weakness that could simply be corrected. I think they should just fix it, as it sounds like they may have.
Which is why I said I agree in general with your first statement.
ETA: It could be that the firing pin design was lightened to keep the trigger pull from getting too heavy. Sometimes with new designs there are unforeseen stresses.
The downside, of course, is the additional nuisance in keeping the snap caps flowing on a striker-fired non-resetting trigger like the M&P (and others).
Depends on what you’re doing. I can get a lot of dryfire practice in without removing the single snap cap from the chamber.
If you’re doing tap rack bang drills, then you should have a snap cap anyway to make sure that you’re doing the technique correctly ejecting the dud round and not shorting the slide. Also if you have another snap cap in the magazine you can tell if you’re riding the slide home much more easily.