There are only a few MFG’s that I am aware of that have some form of firing pin block and only on certain models. On a FULLY functional 1911 it is physically VERY hard to get it to go off by dropping it. The grip safety physically blocks the movement of the trigger. So if you have enough inertia to move the grip safety forward that same inertia would also keep the trigger forward. If the grip safety is forward it does move the sear and disconector into firing position. So the thumb safety would have to be off and it would have to land nose down and the trigger would have needed to have been modified below safe standards to get it to bounce off of cocked. Conceptually the half cock SHOULD catch the hammer because its not at full spring pressure.
Is it possible? Yup! Is it likely Nope!
As for setting the gun off while chambering a round I call BS. There is not enough inertia in the firing pin to override the firing pin return spring.
If you want a look at the RIA check this out. The gun was fine out of the box but I can’t let a 1911 sit at good when I know what I can do and what I prefer.
Cheers,
Craig6