Spotlight appears to work for the root pool but not for child filesystems. This is probably because there is no way of reconciling the filesystem with a device minor ID in an easy way.

Further it seems that spotlight only looks at mounts with local and !nobrowse settings, which aren't set at present. There's also some finder option that can be set to disable showing them in a carbon call if otherwise polluting the space

MacZFS has been discontinued. Please switch to https://openzfsonosx.org/