Was there any reason the multi-part movie merge logic was updated?

[sxales]

It appears between 10.8.13 and 10.9.7 the logic that merged multi-part movies was updated. As a result, A,B,C suffixes no longer merge.

In 10.8.13, the following movie with multiple parts are merged into a single movie (with additional parts).

Title (Year)/TitleA.mkv
Title (Year)/TitleB.mkv
Title (Year)/TitleA.nfo
Title (Year)/TitleA-poster.jpg
Title (Year)/TitleA-fanart.jpg

In 10,9.7, TitleA shows up Title (Year) with metadata but TitleB lists separately with no metadata.

I don't see anything mentioned in the change log or a recent issue to explain why this change was made. Is this just an undocumented change in behavior going forward, or was this unintentional?

[theguymadmax]

The change was in the initial 10.9.0 release. Here is the pull request explaining the changes. Basically there should have been a space after the movie followed by (parttype) in the naming structure. This was being ignored by the file stacking rules, now it's enforced.

So in your case it should be:
Title (Year)/Title partA.mkv
Title (Year)/Title partB.mkv

[sxales]

I love when people change behavior that has been in the system for years because they don't like the way it looks. Now I get to go rename a couple of hundred files.