I think when people say 'downgrade', often times its because they see gameplay or something that for whatever reason, isn't as impressive as what they've seen before. Maybe they don't have the capacity to actually pinpoint exactly what it is they feel is downgraded, but they do know that they aren't impressed and their first instinct is to question whether the game was downgraded, as its become something of a buzzword this past year or so.
That's not necessarily concern trolling. I must say, I've seen aliasing in screenshots of this game before and everything, but this is the first time I've seen it quite so noticeable in video. Now, I don't know if they've somehow been messing with a different AA solution from before or what, but my first impression on watching the video was definitely, "This does not look as good as what I've seen before." I don't know that it was necessarily downgraded, and I think people should definitely be careful throwing that word around, but its still not necessarily concern trolling. Concern trolling is when people chime in with 'concern' about something they're actually not concerned about at all. But I reckon some people are seeing this video and are genuinely a bit concerned at the graphics. Claiming 'downgrade' may not be the best way to express that, but it doesn't mean they're trolling.
Then of course begins the hunt for what was actually downgraded, and if nothing turns up, then you can claim that there's no evidence of it, but again, whether its concern trolling or not is based on intention, not expectation levels or being harsh or being incorrect.