It's definitely visible in GT7 in daytime races, less so night time. Daytime races the roads are more grey than black and you can see it on them. Car interiors also have some slight mura. It's going to be less noticeable when there are lots of cars around or there's less open terrain in the middle distance. I've tested 3 different headsets at this point and they all had visible mura in GT7, one (defective) being worse than the other 2.
I really do think some people just have very limited sensitivity to it. Some people don't notice banding or DSE on TVs either. Wish I was the same.
Another key thing here is are you trying to focus close and look right at it or are you reporting how it looks when you are actively playing the game.