That’s literally what I’m saying; It’s fine as long as there wasn’t any unwritten data in the cache when the machine crashes/suddenly loses power. RAID controllers have a battery backed write cache for this reason, because traditional RAID5/6 has the same issue.

BTRFS RAID5/6 is fine as long you don’t run into a scenario where your machine crashes and there was still unwritten data in the cache. Also write performance sucks and scrubbing takes an eternity.