Factory +P is tylically a 125 JHP at 925 FPS. Big whoop. This is not hot. It's not even warm. It's less pressure than the standard loads were prior to the lawyers taking over to fight off other lawyers out there suing everyone in sight.
No ammo company would sell any ammo that would damage or excessively wear a quality made gun. A post-war M&P will not be worn by +P. None of mine have been so far.
Factory +P is loaded to pressures well below industry maximums for the caliber.
Yes, S&W says not to use +P. They always say this no matter what gun you ask about. Just for fun call and ask them if +P is OK in your Heavy Duty 38/44revolver. They will say no because that's what their lawyers tell them to say even though original 38/44 ammo, which works fine in all S&W revolvers, was much hotter than current +P.
Do all what you want, but don't try to tell me factory +P is a hot load or is dangerous or will even wear the guns. It's a moderate load, at best.