A BM move in chess turnout to be a brilliant move (+a disgusting engine puzzle)

Bf8 !! I don't know why engine like it so much but for me it's just a "badass move"or "a complete BM of a move".  Anyways, it's only +3 for a brilliant move which is not a completely winning game for white. Can you find a great defensive move here for black? Note that black will still be losing anyways after this move.

Nd4... No time for Nxa1 obviously, But there is time for putting a knight on f3 disconnecting the rook and pawn on f6 so then the queen can later capture the pawn on f6. That's a somewhat reasonable move to find, But the next move is what shocked me the most.

Nef3... here is where it got really confusing since Ndf3 actually doesn't work. So, can you figure this thing out why Nef3 works but Ndf3 doesn't?

(Potential) answer in white text: is it that the queen needs the e5  square after gxf3 Qxf6 Nh4?

there might be some lol