You guys are completely off. The ACC system absolutely can and does use the friction brakes, just as it does in every other non-hybrid Ford/Lincoln model. The stability control system also applies the friction brakes when needed using the same hardware. However the system can not apply 100% braking power, it only can apply something like 20% of maximum braking, that's why the warning will come on when using ACC sometimes. What might have you confused is that the brakes (friction or regen) are only applied while ACC is active, not when ACC is off and the collision warning comes on. From what I've heard, the main reason the Ford system doesn't do a full stop is because it can't do it smoothly and quietly. Once vehicle speed gets low there isn't enough background noise to drown out the actuator motor sound so Ford figured people would complain and think something was broken. They must have resolved it though, since the 2017 Fusion system will have full-stop.
As for the Tesla system, well Tesla doesn't have any unique hardware, their lawyers just don't have as much experience as all the other OEMs yet.