KERML_ — Use of memberName in OwningMembership

In section 8.3.2.4.5 - the spec says
A Namespace can provide names for its members via the memberNames and memberShortNames specified by the Memberships in the Namespace.
However, the only subclass of Membership, OwningMembership redefines memberName, thus:
8.3.2.4.8:
/ownedMemberName : String [0..1]

Presumably this means that effectively memberName must equal ownedMemberName in OwningMembership.
There is no constraint to this effect and i can see it would be tricky, give the redefinition.
I wonder whether the metamodel needs a bit of surgery, given that the majority of Memberships are OwningMemberships and therefore have this issue.