I mean, Cameron is a douche, but he's right in this case. There's a lot to complain about with his body of work, but grain levels just aren't on the list.
It's a straw man. A lot of the 4k cameron remasters are not good. Color correction being extremely off being one of the biggest sins.
Also. His argument is awful "my team has done this forever"... Well they've done it wrong, guy. Literally have not heard of any other movie getting criticism for a 4k remaster except his
They focus on the grain reduction nagging in Aliens when that was not even that big of an issue.
My main problem with these recent 4K releases was True Lies, it has straight up AI hallucinations in it, I really doubt he rewatched the final product at all.
The grain isn’t the issue. They are straight up AI upscales filled with artefacts and barely any use of HDR colour capabilities. Fan edits have done better jobs.
He made some really good movies barely watchable with AI upscaling. Imagine walking by a bridge construction and you ask the guy responsible why the two ends don't line up and he says: get a life loser, i build a lot of bridges.