If OP is backing up locally onto a ZFS server like they said they were then say propagating this data to a cloud provider like Blackblaze which uses ext4 this sort of approach makes sense.

This approach is also good when you have multiple sources to restore from. It makes it easier to determine what is the new "source of truth."

Theres something to be said too for backing up onto different FS too. You don't want to be stung by a FS bug and if you do then it's good to know about it.