Skipping unmounted datasets is confusing and not documented.
I see that a change was made in https://github.com/bdrewery/zfstools/commit/3628f79db4fbf9bb79d8bdfbaade7544ba08b22e (and modified a few times since) to not snapshot unmounted systems, but this is confusing to me because I had explicitly set the com.sun:auto-snapshot=true flag as required by the documentation.
I have a problem now that I cannot apply recursive rules to snapshots because there are none of the relevant name on the root dataset.
Maybe if you want to preserve the existing behaviour can we have an additional flag for com.sun:auto-snapshot like force which does the snapshot even if unmounted?
I also have this problem but luckily personally have been able to get around it by mounting the parent node as "/mounted-for-the-purpose-of-auto-snapshot". In other setups I wouldn't be able to do that.
I think this issue should be considered. The current behavior can be problematic.