I suspect that the Navigate to Barline commands aren’t hooked up to anything yet. They don’t work for me either.
For me ⌥⇧Space plays a short note wherever the playhead is, and stops, and the timer doesn’t advance. I think the reason for this is that Scrub Playback is now assigned to ⌥Space, and it’s interfering with Play from Start of Flow, with the result something like “scrub at last start position”.