The change was very simple and isolated, finding it was the real problem. Once there, all the behavior made perfect sense. So I don't expect any side-effects from it. Essentially, when it was grouping up things for a single Blu-ray aggregate (as part of the changes to improve this in MC30), it was checking for things to start with W:\Movie, instead of W:\Movie\, hence "movie series" being affected, as they shared a common path fragment. This change alone should not have any other impact.
The naming of index.bluray is intentional and how Blu-ray structures have historically always been named - except for a brief period where a bug with the extended video analysis overwrote the name to index.bdmv.