The thread was created in the Mail Gateway forum - I moved it to the more appropriate PVE subforum.
Regarding your question - if you install FreeBSD inside the guest - it depends on how FreeBSD partitions the disk - so I assume that FreeBSD simply did not do the alignment (and would not be too scared about that in general).
In any case it's nothing that can be "fixed/repaired" from the PVE side
You didn't mention what the backing storage is, I'm assuming SSD. Keep an eye on the wearout indicator in the GUI and SMART table, you /might/ be getting excessive write amplification.
However, I get the same error when I do that on the host, so jury is still out on if it's actually problematic. My nvme wearout on 2x SSD is at 1% and 0% and the node has been running mostly 24/7 since Feb.