Comment by wkat4242
ZFS also had expansion for a long time but it was offline expansion. I don't know if btrfs has also had online for a long time?
And shrinking no, that is a big missing feature in ZFS IMO. Understandable considering its heritage (large scale datacenters) but nevertheless an issue for home use.
But raidz is rock-solid. Btrfs' raid is not.
Raidz wasn't able to be expanded in place before this. You were able to add to a pool that included a raidz vdev, but that raidz vdev was immutable.