Exactly, being a demonstration of the game, it is likely that the full version will be the same in those regards.
That demo was given to journalists a long time before it was on PSN...and during the time with journalists such as IGN, it was revealed that they were starting to get the game running in 1080p.
It is highly reasonable to suppose that the demo on PSN remained on a previous lower resolution, since they wanted it to be clean and a good representation, while they worked on getting the game engine running well at 1080p.
Whereas your argument seems to run on emphasising linguistics...