Chewtobacca said:
Didn't Japanese NTSC use a different black level from North America?

After 1990 they did.

601 was first published in early 1980's, during the time when Japanese NTSC hadn't evolved yet. Was still the same as north American standard.

These Special Collection discs were mastered in the later Eighties, so they still used 7.5 IRE units for black. Well I can't prove it, but I think so.
Seems like 601 should apply here...

Makes me think of Karyudo at times like these. Well Happy Christmas Karyudo wherever you are :)