Maybe?
I’d guess the question of “which layer controls the clock” probably varies by application.
For something like mlr, supercolider has a much better idea of where the beats fall. Particularly if you’re not quantizing every button press. So, I’d imagine it would send messages back to lua when it’s time to update the interface. Ableton Link at the supercollider level seems perfectly appropriate there.
For a simple step sequencer, where each beat triggers a new event to occur, it might make more sense for that to be handled in lua.
…maybe.
Some experimenting required. But I feel like “the clock isn’t an interface element” might be the way to look at this.