it's actually located under screenshots and not concept art on their site.
That is correct, therefore, logically, it should be an in-game screenshot, unless Bethesda is trying to mislead us by passing off something that is not actually in-game at all as a screenshot, which they have not done before, besides, if Bethesda wanted to mislead us into thinking that the graphics are better than they really are, the first thing they should have done was not show us the rapids in the trailer, there are also some flaws in it that wouldn't need to be present with something that wasn't rendered in real time, so I can only trust that it is indeed a screenshot, albeit one of the more impressive ones.
It looks a lot more CGI-ish than the other concept art, too.
That is also true, the style looks nothing like any of the other concept art at all, if it weren't a screenshot, it would likely be a 3D render created for promotional purposes, similar to the teaser trailer (Not the one with actual gameplay.)