Unsurprising. Red Hat has not hired upstream Btrfs developers for years, where SUSE has hired bunches. Meanwhile Red Hat has upstream ext4, XFS and LVM developers.

If you're going to support a code base for ~10 years, you're going to need upstream people to support it. And realistically Red Hat's comfortable putting their eggs all in the device-mapper, LVM, and XFS basket.

But, there's more: https://github.com/stratis-storage/stratisd

Btrfs has no licensing issues, but after many years of work it still has significant technical issues that may never be resolved. page 4

Stratis version 3.0 Rough ZFS feature parity. New DM features needed. Page 22 https://stratis-storage.github.io/StratisSoftwareDesign.pdf

Both of those are unqualified statements, so fair or unfair my inclination is to take the project with a grain of salt.