[live.thisdevice] is where that comes from.
I don’t remember offhand which outlet is which, but one of them gives you state info (“this track is selected” vs “this max for live device is selected” vs “neither of those are selected”). I’m sure he’s using that.
I think the left outlet is your “ready to execute” message. (the max for live version of “loadbang”) Which is what you’re looking for.
The problem is this:
If you tie into that event, and your setup has 20 autofocus devices, which one gets control when you open your scene?
The answer is each of them, very briefly, in the order that they finish loading.
That’s not a great answer.