Just a guess but my experience is that hammer fired semis feel deferent than striker fired ones. I have two Sigs both hammer fired and in double action mode, first round, they have a stacking feel similar to a double action revolver, which have no safeties. The striker fired M&P 2 in 9MM doesn't have that "stacking" feel and if you've trained and shot extensively with hammer fired pistols it may be easy to unintentionally discharge a striker fired semi. Kinda like going to a GP shift pattern from a normal one.