Comment 11 for bug 1858201

Note we can derive that allocation was not set as we see "-s" (capacity != allocation), but we don't see -o so allocation is "0" (likely unset).

330 if (vol->target.capacity != vol->target.allocation) {
331 virCommandAddArg(cmd, "-s");
332 if (vol->target.allocation > 0) {
333 virCommandAddArg(cmd, "-o");

Further we have:
339 virCommandAddArg(cmd, "-V");
340 virCommandAddArgFormat(cmd, "%lluK",
341 VIR_DIV_UP(vol->target.capacity, 1024));

Currently the code makes whatever you pass it 1k aligned (unconditionally).
That is in src/storage/storage_backend_zfs.c.

Code-wise it would be easy to make it 8k aligned, but I'd need to know if that is a general ZFS requirement or just one due to the way you set up your ZFS.
Note: the code is that way since ZFS support was added in 2014, not much changes going on.

But I start to guess too much ...
Still waiting for the commands and XMLs that got used to reproduce this as asked before.