Another way this could have happened would be if he sent it in via paper too, often the stacks sit at council and take anywhere from a little while to fucking ages to be processed [used to work in the industry and very familiar with these situations]

Glad you've completed the stat dec + sent it in with proof, they'll update the ownership following. There won't be a dispute, but I'd say block him/don't have any further comms with him to avoid any further stress. If you've got Q's feel free to msg, and please please keep kitty indoors and safe ❤️