One more time, from someone with audiophile cans who is claiming it is:
"To to start, these aren't completely neutral. There's a
bit of fun to them, but it's nothing like the XM4s that had that fairly huge boost to anything below 120Hz. Sound-stage wise, these are some of the most impressive closed-backs I've tried. They're pretty equivalent to the Fostex in sound signature: A little bump in the bass but nothing silly. There's a bit of sparkle in the cymbals but nothing ear-piercing. They sound better than the Momentum 2s, and I actually prefer them to the Fostex. I like them about as much as the 6XX, which is saying a
lot. They sound a lot
faster than the 6XX too, although not as quite as fast as the Fostex."
https://www.reddit.com/r/airpods/comments/kd9hgz
Yes, the XM4s are the market leader, and of course much of that is due to overall combination of features and value.
When you move up the audio food chain diminishing returns sets it, that is not a mystery. Typical $4k cans are maybe only 5-10% better than $2k cans, for instance.