Ok playing a SnG recently and I get

in the BB. I check with 3 limpers.
The flop comes

. I bet 1/2 the pot and get one caller.
The turn is the

, giving me a straight flush. I check, the other guy bets 1/2 the pot and I call.
The river is a blank and I bet enough to put him all in. He calls. Obv I win the hand.
However, what was interesting is after the hand someone said 'vnh, always nice to have the nuts'. To which another player responded 'he didn't have the nuts,

, was the nuts". I said "lol ok" and continued as I was 3 tabling.
After the set was over I thought about what he said.
Is the nuts the best two hole cards you could have based on the board, or is the nuts an unbeatable hand?
Just curious