They could've realocated resources from the other versions to get all ready at the same time.
I agree actually. I'm getting it on PS4, but
if the Switch game really is just the PS4 one, not launching at the same time seem like a really bad move to me.
Sure, they will get some double dippers, but not many. This is an eighty-ish hours long epic, not many people are going to be interested in replaying it within a long ass time of their first experience. If it's six months later, the amount of people who are going to be ready to re-up at that point? Not many at all I'd wager. So you're not gaining much for double dips, and you're losing the advantage of releasing within the main marketing campaign. Seems like really poor idea to me.
EDIT: Unless they don't give a shit and they've just sold the publishing rights in the West to Nintendo, then they don't have to worry about any of that.