I would assume Reid's issue is that they don't usually call it on an inch or two.
This was the play
He's right on the 49 yard line. The ball is maybe an inch behind the 49 yard line? And that's after the center picked it up which typically the center picks it up and moves it back a little. If you look at the chains on the sidelines it looks like it's right on the 49.
On most plays a WR is either technically offsides or technically not on the LoS that is supposed to be compared to where the center has the ball. They usually just call it close enough as long as the guy isn't off by like half a yard in one direction or the other.
Doesn't really look much different than how Von Miller was lining up on about 50% of the plays all night long, which I think is what Mahomes was peeved about.