The way I've always thought of it is that if you were playing on the TV you have the nuts when they give you that tick next to your name.
when you watch poker on TV and they put a check mark by the players name . that does not mean they have "the nuts."
it just means they can not be beat.
not every hand that wins a pot is the nuts.
the nuts to me is the best of any given hand.
Ace high flush is the nut flush.
Ace high straight is the nut is the nut straight. etc..
but it doesn't matter . you can flop the nut flush, and still get beat by a full house or whatever. but you still had the nut flush.