If you're going to choose a specific handgun, it would seem prudent to be as thoroughly familiar with not only the way it operates and is supposed to be safely manipulated in ordinary non-stress situations, but anything about its manipulation and function that might present a potential disadvantage during chaotic conditions.
Training acquired in dealing with specific situations might prove beneficial, too, but how many people ever encounter any actual conditions more stressful than putting holes in paper or cardboard targets on a controlled range?
Kind of like learning motorcycle riding skills in a large parking lot, and then hoping those will somehow successfully translate to being "accessible" to you if you encounter an actual emergency situation on the road, at faster speeds, in worse driving conditions and especially involving other traffic.
FWIW, I've watched more than one strong young man discover during a "minimum stress" qual course-of-fire that he wasn't obtaining a grip sufficient to depress his grip safety, and wonder why the 1911 didn't fire even though the thumb safety was OFF.
The 1911 design usually requires bit more familiarization with someone operating both the grip safety and the thumb safety, and having the requisite skillset and experience to maintain awareness and control of both "safeties", including manipulating and operating the gun under stress.
The same could be said of the importance of being thoroughly familiar with the design, operation and intended function of other types of handguns, including revolvers and other pistol designs.
After all, even just considering something as "simple" as having someone "make a fist", and perhaps even learning how to strike a padded practice surface or a heavy bag in a way that doesn't cause them to experience injury. Does that mean they can effectively do it under stress?
It's arguably quite another thing for them to be able to make a proper fist in the chaos of an unexpected and stressful real-life encounter, as well as be able to deliver the fist blow properly, on the intended (and appropriate) anatomical surface, without breaking their hand or injuring their wrist .. let alone do so rapidly and effectively enough to achieve their purpose.
Why would the importance of skill, ability and experience in an unarmed fight be that significantly different than having the presence of mind, ability and experience to use a handgun if involved in a gunfight?