Yes, cashback generally is turning a bit scammy/cancelly. However, just eat / dominos work well and post very quickly. Anything consumable can’t be returned 14 days later so they have no reason to wait for cooling off periods etc before posting the Avios. Hotels are worst because you normally have to wait until a couple of months after your stay, and normally they mess up the IT and cancel, especially if you’ve made even the smallest changes to your booking (breakfast, bar charges).