BB should send CC#102 when a song is first started or even a new CC# specifying what part the song started with.
The scenario, you have a MIDI controller with 4 buttons each assigned to a song part (transiton) and your song has only 2 parts, you press the button that would start you on Part 4, BB will start on Part 1 (because Part 4 doesn’t exist) however there’s no feedback that it started on that part 1 and there’s no way to get the number of parts of the song from BB for MIDI controller to know if you are trying to start in an unexisting song part.
This allows for better 3rd party software/hardware syncing, expanding the usability of BB
Also CC#102 doesn’t seem to be sent by BB when the MIDI OUT is set to MERGE.