I recently purchased a collectors edition copy of Legion on my main account and when I received the notification saying my mount and pet were ready to be accepted I clicked them, they went into my bags and I logged off that toon. However, I went to do a character transfer from the newly legion account to another account that didn't have legion. After receiving multiple errors trying to do this on my own I asked via live chat and was told it was due to one copy having legion and the other not. So they refunded legion to allow me to do the transfer and then I simply added back the standard edition of legion after changing my mind on the pet and mount. To my surprise when I logged back in there they were sitting in my bags still just waiting to be clicked and added to my collection.
TL:DR - Buy collectors, loot mount and pet, request refund, buy back standard edition, log in and learn mount/pet profit.
TL:DR - Buy collectors, loot mount and pet, request refund, buy back standard edition, log in and learn mount/pet profit.