this report is for FreeNAS-11.2-U6, which runs on kernel 11.2.
If I try to create a jail via CLI/iocage for release 11.3, it results in the following message:
Host: 11.2-RELEASE is not greater than target: 11.3-RELEASE This is unsupported.
This is expected. If I create a jail via GUI, it offers me release 11.3, I can choose and it seems to succeed. In the listing of existing jails, it is then shown as an 11.3-release jail. As far as I understand, this cannot be true and has to be some kind of GUI-bug.