FreeNAS Mini with 12.0 Nightly installed.
Created ZFS encrypted pool, pool2, and set passphrase testing123 on it. Created encrypted dataset testing1234 and set passphrase testing1234 on it. Locked testing1234, then locked pool2. Tried to unlock only pool2 by unsetting Unlock Children and entering the passphrase testing123 in the only field for pool2.
UI warns that dataset testing1234 will not be unlocked. I click continue, then the operation errors out with the message "Passphrase or key must be specified for pool2/testing1234" displaying on the unlock screen.