Actually, in the last 6 months or so the way that CIFS shares calculate free size has changed. ;)
FreeNAS itself has gone through several WebGUI changes for the volume page, so you can't even trust that numbers you saw 2 years ago came from the same source as they do now. :(
So yeah, everything you've just mentioned is variable. So unless you have a screenshot of "zfs list" and "zpool list" from 2 years ago and then the same output right now there is no "good comparison". :/
FreeNAS itself has gone through several WebGUI changes for the volume page, so you can't even trust that numbers you saw 2 years ago came from the same source as they do now. :(
So yeah, everything you've just mentioned is variable. So unless you have a screenshot of "zfs list" and "zpool list" from 2 years ago and then the same output right now there is no "good comparison". :/