Most people only have a foggy notion of how fast a really good ABS setup can stop a vehicle. That's why most people trying to "test" their AEB system either can't make it work or discover they need clean underwear after getting it to work. The ADAS and ABS know exactly how quickly they can stop you, and in the interests of being safe but not annoying, they won't resort to AEB until the last instants of "collision avoidability". That interval is way
shorter than most of our brains imagine.