Two examples that I can find are https://github.com/openzfs/zfs/issues/7910, where very old versions of ZFS appear to have quietly written slightly incorrect ACL information, and https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/190... where Ubuntu 21.10 shipped with a bug that created corrupted ZFS filesystems. I believe https://www.illumos.org/issues/9847 may be another example of this, although less severe, where ZFS leaked disk space under some circumstances.

> Two examples that I can find

I think you may be misreading my point above. I am not arguing ZFS doesn't have bugs. That's nuts. I am arguing that the bug the parent says he has would be an extraordinary bug.

This is not just a bug that a scrub wouldn't find, but also it is a bug which an fsck would find. And it is not just a bug in the spacemaps or other metadata, but the parent's claim is this is a bug which a scrub, which is just a read, wouldn't see, but a subsequent read would reveal.

Ubuntu shipped with a bug that they introduced by way of a very badly done patch. While I get your point, I don't think it's fair to use Ubuntu as a source - they're grossly incompetent when it comes to handling ZFS.