If you get Legacy at an outlet, it would go in a Legacy thread, definitely. I wouldn't put it in an outlet thread.
I think the reason some wanted an outlet thread is because while they do carry normal, out of season, boutique bags, they also have certain items that are only made for the outlets. So they wouldn't necessarily plug in anywhere else.
Well, even the ones made expressly for outlets are still part of the normal lines, (Soho, Hamptons, Chelsea, etc.) so if you wanted to you could just include those items in the regular threads, but with a note that they are outlet exclusives, nor boutique product.