I'm very a much new to ZFS and FreeNAS myself but what I've been reading is that if you hit the upgrade button for your volumes (as pictured below) after installing Corral you can't simply import those volumes back into FreeNAS 9.10 because that upgrade button introduced some features only available in FreeBSD 11 where 9.10 is based on FreeBSD 10.I had created a pool in FreeNAS Corral (Virtualized under esxi 6.5). I created new VMs with 9.10 and napp-it and passed through the HBA to the new VMS. I was able to import them. I'm a complete neophyte when it comes to ZFS and dont understand what you mean by update the pools within Corral.
What version of Corral are you on? I'm on 10.0.2.