It does have the former, these days - the "allocation_classes" feature lets you make the permanent home of certain subsets of data on "special" vdevs - which in

It does have the former, these days - the "allocation_classes" feature lets you make the permanent home of certain subsets of data on "special" vdevs - which includes methods of specifying "store dedup table there". Now, that becomes the only place entries on it are stored, so you best make it redundant if you don't want to lose your pool from a single NVMe failing, but the feature is there. The latter I would predict seeing approximately when the sun burns out, on ZFS. It _really_ doesn't like the idea of data changing locations retroactively.