Yeah, I'd say that's just some compression trick as well.

If I want to go down the road of a grand conspiracy, I'm at coercion due to blackmail, hostages, etc. long before I'm at the assumption that they put together a fake of such quality we are only able to tell by pixel peeping around his collar.

Also most deep fake tech as I understand it would only introduce artifacts around the face and places that it directly covers-uncovers as it moves. So I dunno which part of the collar OP is looking at, but 90% of it should be unaffected by facial editting software. Glitchy bits elsewhere are much more likely video compression than anything nefarious.