Yes, after move 5 there are definitely some endgame positions that are lost for black.
But it's move 5 and the opponent will be working against you for an entire game. It's not as if every endgame is bad for black.
That said, accepting (even if it's so minor) a structural defect after NxN has always seemed a bit dubious to me, no matter the opening. Some players even recapture with the g pawn there!
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