According to the 1.7 release notes:
"This release also includes 2 changes on the album screen.
First, multi-disc sets up to 200 tracks will now get a new All Tracks tab. This view will allow you to view the entire album in a single list, which should ensure better presentation of multi-part works that span multiple discs."
@support Why the limit?? With the new SECTION tag when combined with PART and WORK you have tons of flexibility to organize large box sets and when you do this, it shines the best in the “All Tracks” tab. But this 200 track limit means you can’t use it beyond 10-20 disc box sets. This is a real bummer. Can we please expand this?