I think the problem with btrfs is that it entered the spotlight way to early. With Wayland there was time to work on a lot of the kinks before everyone started seriously switching.
On btrfs a bunch of people switched blindly and then lost data. This caused many to have a bad impression of btrfs. These days it is significantly better but because there was so much fear there is less attention paid to it and it is less widely used.
If that is the case, then you can probably easily find the X server code in the Linux kernel and send a link? Spoiler: it is not there
@hummus273 I am mistaken, it is only the mode setting for the X-server that is handled in the kernel. At any rate it works well for my needs.