I have been saying that exact statement about aim assist with Xim for years.
It's also amazing that when you turn off AA in some games ( Division 2 for example ) the bad aiming system in the game suddenly isn't anywhere near as bad.
Micro aim adjust around enemies in that game are notoriously bad with Xim KB/M, but if you turn off aim assist all of a sudden those micro movements are much easier and smoother.
The Nexus does a better job with that game in general, but that is not to do with aiming, it is to do with general movement, Like turning while in sprint, the right stick makes it very easily controlled , where Xim KB/M requires a lot of messing with either turn assist or in my case an aux config.
Something I have noticed is the game is very different when played on my XB1X compared to my XBSX.