Lucas has to be misrembering things too. Jabba wasn’t designed as a slug until ROTJ when a bunch of different maquettes were presented to him. So the idea human Jabba was going to be a Slug stop motioned in, that can’t be correct.
If the scene was kept in 77 Declan would have been in the movie.
A bunch of stuff he said at Cannes is just malarkey. Complete and utter BS.