And to preempt an argument... "there's no study that says beards/razor bumps interfere with gas masks"... There are. Most of them say minimal beards/hair is fine (less than 1/16th of an inch) to get a mask seal, where 1/8 can already lead to issues. But it's understudied. The risk of getting it wrong is people's lives.
I was coming in here to disagree with you, because I've heard this same thing, but I won't argue a point unless I check my sources first, and sure enough, you're correct (except maybe that stubble is fine). OSHA even states that tight-fitting respirators are not to be used by those with facial hair that extends past/across the seal. So one could argue that if wearing a gas mask is a requirement, anybody who has facial hair (other than a trimmed moustache) is unable to fulfill that requirement by OSHA rules alone.
I think a simple matter that if you roll around on the ground "in pain," you get removed for medical attention and for the rest of the game for monitoring. If you're injured, you're injuried. If you're being a whiny baby, you don't deserve to be in the game. If you're faking, you deserve to be ejected. But in all cases it comes to the same conclusion.
Oh, and this doesn't automatically mean a foul. It's not like a person can't get hurt when no foul occurs. I hurt myself stepping out of bed in the morning.