A gore or nsfl tag is much more important than a porn one. The disturbing shit that will haunt my nightmares is what I want to keep off my feed, I'm not particularly worried about accidentally seeing some genitals.
But I don't think an X-RAY would even qualify as NSFL, would it? I mean you see that factually, that probably hurts, but you get zero impression of it.
Kinda like fotos of the atomic bomb explosions from WW2. You know some people are suffering in the very moment that foto was taken, but you can't see it, so it's not NSFL.
Or do you have a dofferent oppinion?