Ever heard of dilute genes?
The Phantom/Mystic seem to be a dilute version of the het BEL gene and thus when combined with another het BEL makes a BEL, but when combined with another dilute het BEL make a completely different super.
As far as crossing the cinny and black pastel its been done and the super looks the same as the super of the black pastel or the cinny. Same gene different lines, IMO.