Obviously, this shows my ignorance, but what's the technical reason that you can't pass the PMKID like Pass the hash?
It is mandatory to request the PMKID from an access point (EAPOL M1) or to retrieve it from a client (reassociation request).
I guess the question was meant to ask "why can you not use the PMKID to authenticate with a AP". Answer is simple: because the PMKID is not used in the WPA handshake.