I notice that the contrib contrib/slapd-modules/samba4/pguid.c related to this ITS defines a "parentUUID" attribute
1.3.6.1.4.1.4203.666.1.59 NAME 'parentUUID' DESC 'the value of the entryUUID of the parent' EQUALITY UUIDMatch ORDERING UUIDOrderingMatch SYNTAX 1.3.6.1.1.16.1 USAGE dSAOperation SINGLE-VALUE NO-USER-MODIFICATION
which is very similar to the "superiorUUID" attribute
1.3.6.1.4.1.4203.666.1.11 NAME 'superiorUUID' DESC 'UUID of the superior entry' EQUALITY UUIDMatch ORDERING UUIDOrderingMatch SYNTAX 1.3.6.1.1.16.1 SINGLE-VALUE NO-USER-MODIFICATION USAGE directoryOperation
defined in servers/slapd/schema_prep.c; although this contrib is not currently used in samba4, I suggest "parentUUID" be defined as an alias of "superiorUUID", or vice-versa, so that "parentUUID" becomes the preferred form.
p.