Yeah its a cinematic sequence but you can tell it is in-game graphics. Even if you look at the non-cinematic stuff it looks better.
Thats also true that because its 4K they would turn down the graphics, but why not turn them all the way up, even if it judders and stutters like mad just to catch the 4K screenshot? Thats what they are doing after all, just showing the visuals in a single image...
The game has deffo been downgraded, there was a recent video of it and it looked poop to what it used to look like. Could of been on consoles but I'm sure it was on PC.