Ok, I’ve had a chance to try it again, and it mostly works as you’ve described. If I hit play and send an articulation change (via program change) twice, it changes the articulation and “unlocks” it, so that it will continue to read and process written articulation changes.
The one exception being: If, after setting and unlocking the active articulation during playback as described above, the next written articulation is the first/topmost articulation (triggered via PC 1), it will not be read and processed.
To me, this edge case feels like a bug (@Martin.Jirsak can you please confirm?)
Without getting into a philosophical discussion on bugs vs. feature changes etc., I will say that this whole process of discovering how the updated articulation system is meant to function has been a chore. I have not found any official documentation that describes this “double-tap” functionality, or anything about “locking” an articulation. At worst, this is buggy behaviour. At best, it’s undocumented. The reality seems to exist somewhere in the middle and it falls on the users to decode which is which.
EDIT: after more testing, I’ve discovered a further problem.
With this “lock/unlock” approach where you have to send PC messages twice, a few undesirable side effects occur:
1 - the Sound Slots list in the inspector resets and does not show which articulation has been activated (and unlocked).
2 (this is the important one) - it is no longer possible to record articulation changes via retrospective record. If I press play, set an articulation twice (so that it is not locked), I can perform notes in this new articulation, but the articulation change does not get captured by retrospective record at all!
3 - It does seem to work with regular (not retrospective) record, but it appears that the “double-tap” records as a reset in the sound slots lane, which creates visual clutter.
I’m still adamant that a previous workflow has been broken in 15. It was previously possible to record articulation changes via MIDI program change, and have those articulations stick until either a new articulation is recorded, or a previously recorded articulation is encountered. This worked with regular record and retrospective record.