So I cloned 4 volumes into a new 1TB APFS Container of 4 APFS Volumes. 1 Terabyte's worth of data to brand new external SSD. After unmounting and remounting the drive: NO DISKS. diskutil listed the container in ERROR. And then Disk Utility automagically formatted a new single volume out of it.
I trusted a little bit eagerly that the claim of hundreds of millions of devices tested upon had a little bit more weight. And unfortunately diskutil and a lack of documentation left few options but to reformat back into trusty old HFS+.
Any reason in particular ZFS was so flawed it couldn't be relied upon? In particular it brings existing tools, deduplication, and data checksumming. That whole container thing just collapsed on me with a nice single error message. And Recovery repair did nothing to illuminate or help