QNAP forked from OpenZFS a long time ago, before the ZoL project was renamed the canonical OpenZFS project IIRC, and has been reimplementing whatever they wante

QNAP forked from OpenZFS a long time ago, before the ZoL project was renamed the canonical OpenZFS project IIRC, and has been reimplementing whatever they wanted for some time. So it's not just a check for check's sake, I would suspect in practice their send/recv is just completely incompatible at this point.