i totally understand your point ilmago, but the chances of that happening (a position where white can mate with just a knight, for example) are SOOOOO rare compared to the chances of someone "losing" on time when their opponent CAN'T force mate with a knight... is it worth is to inconvenience people 99% of the time for the 1% that would be more "correct"?
I think so, yes. (Granted, you weren't asking me specifically, but...)
ilmago, is there any server which has implemented perfect draw-claim rules?
EDIT: It's extremely common to just implement "mating material is knight + bishop and better".