Btrfs has a broken by design on disk format. Btrfs went with self describing checksums inside blocks instead of a Merkle-DAG with a round robin root. In doing so they ignored existing research at the start of the btrfs project and the only fix is to change the on disk format to add the children's checkums to the parent nodes.
That doesn't sound "broken by design" to me, just less thoroughly safeguarded than ZFS but still more than almost any other filesystem. It's completely consistent with my claim that btrfs isn't trying to follow exactly in the footsteps of ZFS. (And it's not like Merkle trees don't have any tradeoffs.)
