“Real life firefights often are now mostly between people with assault rifles, which are much easier to lead with than pistols, and strafing doesn’t match the protection cover gives, but in a limited cover environment, strafing is almost absolutely necessary to not die.”

Yeah, it was referring to military fighting.

In a close-range fight, of course going prone is useless. You should immediately move for cover. If there is none, just stand and shoot, it’ll be over in a matter of seconds anyway, and jittering around isn’t going to do you any good. Under no circumstances is strafing back and forth in the open a good idea in real life.

I never resorted to walking into walls after playing Portal so maybe I got better? Don’t let me anywhere near Mirror’s Edge!

I don’t know anything about real combat, but I think the original quote was not referring to military fighting. Obviously, hitting the ground is the best bet in that situation due to, as you say, the marksmanship of the enemy and the accuracy of the weapons. I would have thought dropping to the ground when in a gun fight with ordinary pistols would not be your best option.

Funny video.