Yes, thank you for your assessment. You're correct that the trap is easily avoidable and the move is not a great one.
The Kostic Trap
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Kostic evergreen !
Some informations :
https://en.wikipedia.org/wiki/Italian_Game,_Blackburne_Shilling_Gambit
Almost everybody who play it call it Kostic gambit or Kostic trap, as he was the first player to deliver it.
White has an edge after 4.Nxe5...
Not easy to play as black...
But sure, 4.0-0, 4.c3, 4.Nxd4 are best and black may be busted...
White's much better after any reasonable move like 0-0, c3, or Nxd4.