"Once lit, the phase indicates nearby drivers should simply follow the car (AV or human) in front of them, instead of trying to anticipate something like a yellow light’s transition time to red."

I dont know what this means but it sounds similar to the green wave light that we have here in the netherlands. All it is is a lit green double wave that tells you that the very next traffic lights going straight will be guaranteed to be green. This way you dont have to anticipate breaking even if you can see the green light has been on for an entire cycle.

This is usefull because you can chain intersections so the worst case is that you have to wait two cycles on the entire chain, coming on and going off.