The biggest issue I have with Phantom braking is there are a lot of sources of it, but the car doesn't tell you WHY it braked. The lack of knowing leads us to suspect various things. An example of this is blaming the forward collision warning setting. But, that doesn't make any sense from a UX perspective. A warning setting should have no impact on any system that causes an action. If I used a setting of early I'd probably experiment with changing it, but I use a setting of medium so I probably won't bother. I'm perfectly happy with that setting for the purpose of a warning so why bother?
The other issue with Phantom braking is different users have different preferences.
As an example I'd like a very basic TACC system that prioritized smoothness over everything else. Where it's job is to maintain the set speed/distance. Obviously I'm paying attention while driving with TACC so I don't want it to brake for vehicles that get too close to the line or for shadows. My preference is for a very radar dependent system where the camera is only used to correct for positioning of the moving objects the radar detects. I don't want the vehicle to even blink at shadow.
With AP I'm a little more okay with phantom braking, and with NoA I'm basically expecting that I'll have significant disagreements with it.
The problem is Tesla won't offer us this easy kind of solution where they tone down the safety stuff for basic TACC or basic AP.
Driving with TACC/AP feels very much like when a timid driver is behind the wheel. Where they get scared by any little thing, and it's not that they're a danger as much as an embarrassment. Even if their actions caused an accident the other guy gets blamed as they didn't maintain distance, and they're like "But, I wasn't expecting that car to suddenly stop in the middle the road".
As to the degree of false braking what I've noticed is its pretty proportional to the situation encountered. Like for example its known that it will slow down for Semi Trailers that get close to the line. I've seen this numerous times, and how much it brakes is dependent on speed differential. Where I typically encounter this is on I5 going to Portland where the speed limit for cars is 70mph, and its 60mph for trucks. For people not familiar with it this stretch of freeway is dominated by semi's. You'll pass hundreds of them which gives ample opportunity for TACC/AP to freak out. It's pretty typical that cars will be traveling at 80mph, and trucks will be stuck behind someone going 55mph. So there is a huge speed differential.
In my experience I typically get a few minor phantom braking glitches of <5mph on every round trip between Seattle, and Portland. I'll get a more significant one like once a trip. For comparison purposes in 2015 I had a Model S with AP1, and under TACC it hardly ever falsely braked doing the same trip. Another comparison is I have a 2019 Jeep Wrangler Unlimited with Adaptive Cruise Control, and I've never had a false braking event on the highway/freeway. I did have an AEB braking event with it though when going down a ramp. It freaked out because it was a sudden drop and it thought I was going to run into the building so I give it a pass on that one. I haven't experienced an AEB event with my Model 3. It prefers to annoy me with FCW. Typically it does this when the person in front of me is turning. It doesn't seem to have any concept of the future.