Yes, it is. But, @reosarevok, this is apparently not obvious!
I still don’t see it, but if you say so.
So it means that several includes would have to be changed into except.
And also many opera release groups were merged in the past, excerpt and full, together.
They would have to be split, now.
I still don’t get the zero without example but for the first one, as I’m trying to translate this relationship to something I can use for my own CD collection, it seems that it should not be used for that example… 
COMPILATION of FINAL FANTASY VII Best Selection is excerpt from:
- CRISIS CORE –FINAL FANTASY VII–
- BEFORE CRISIS –FINAL FANTASY VII–
- FINAL FANTASY VII ADVENT CHILDREN
- DIRGE of CERBERUS –FINAL FANTASY VII–
I think we could not set the relationships above because for example if we take one of the big release groups, like FINAL FANTASY VII ADVENT CHILDREN:
- FINAL FANTASY VII ADVENT CHILDREN has an excerpt: COMPILATION of FINAL FANTASY VII Best Selection
Then here we see it is strange because the excerpt release group (COMPILATION) contains many recordings that are not in the supposedly bigger release group (ADVENT).
A has excerpts B, C and D is totally possible (several different excerpts of the same big RG), but it should mean that:
- All B recordings are taken from A
- All C recordings are taken from A
- All D recordings are taken from A
- No other recordings than those in A should be found in B, C and D
Of course I think we could allow a small portion of exceptions (bonus tracks) on either sides.