RAID-Z expansion is being worked on:
https://github.com/openzfs/zfs/pull/8853
Last I checked BTRFS RAID5/6 was a dumpster fire and unusable in production. Have they actually open sourced the ability to fix bitrot detection with mdraid? If not, it's kind of irrelevant.
So... once again down votes without response - BTRFS raid still isn't recommended and the file healing isn't compatible with MDRAID I assume and you just don't like the fact I pointed it out? The "I'm downvoting because you pointed out a flaw in my logic" @HN is disappointing.