I understand all of that. None of that disagrees with what I have said. I think we're talking past each other. In a practical sense I agree the two filesystems

I understand all of that. None of that disagrees with what I have said. I think we're talking past each other. In a practical sense I agree the two filesystems achieve an essentially identical result through very similar methods, as you have said. I am making a point specifically about the details of the implementation logic of the two filesystems. Bcachefs (as I understand it) combines multiple smaller blocks into a larger extent. ZFS only has one raw record and its corresponding on-disk compressed record, whose size is rounded up to ashift.