Lining Up Incorrectly on a FT

[Spence]

A1 shooting first of a one-and-one.

A2 lines up in the bottom spot. B2 lines up next to him. Obviously B2 should have been in the bottom spot and A2 should have been in the next slot.

Administering official doesn't notice it until A1 shoots the FT. Blows whistle - calls double violation.

Correct way to handle it?

Is it the officials responsibilty to make sure the players are lined up correctly? I said it was but I was told that its ultimately the responsibility of the players.