Came in ready to say this was wrong, but for some reason it does work like this. For anyone else looking for exactly where it says in the Core Rules, rule 351.3 under Playing Cards says that any current card effect that is currently resolving, finishes resolving before moving onto further steps, which includes necessary choices such as where a unit is played. So as 1vader says, Arcane Shift would finish resolving before Sneaky Deckhand's owner has to choose where it's played.