You're absolutely right...there is a big difference between niche cases and general policy. (I promise I wasn't trying to be evasive, I'm just trying to avoid dragging an argument from another site over to this one so I was being vague.)
Elsewhere, this argument is about players who want more rules to insulate them against the DM...who, for some reason or another, is considered to be the chief obstacle between The Players and The Fun.
"No, you can't do that to my character because the rules clearly say that spell is (reads a paragraph out of the PHB). Check and mate." (high-fives the players to his left and his right)
I mean...what the heck is that all about? I think I'd rather send everyone home and play Skyrim alone, than try to DM that hot mess.