It's quite hard to see the brake lights ON on the screen while driving in daylight (much more visible at night), but they do light up. As far as they turning on, they always do on regen, and when stopped, regardless if you're on AP, FSD, or nothing. So they turn on actually earlier than on ICE cars, since any 'motor' braking (regen) at all, turns them ON on Teslas. I think that's better than too late, but it might be a bit disconcerting at times for traffic following us. I think if you're applying even a hair of throttle, like on a steep downhill, they turn off, even if you're actually doing some regen, but haven't confirmed that.