Funny you should mention that as my car had a flutter a few days ago when driving in human control at about 30mph down a road with a high wall to my left that was close to the road and a large agricultural (I think sprayer) passed going the other way.
It didn't brake but reduced power for a short time (blip). I guess the close proximity of the wall and oncoming vehicle was picked up by the radar but didn't pin my head to the windscreen as the much discussed "phantom braking" was wont to do.
It's often hard to know what different people are experiencing under the heading of "phantom braking". I have the impression that in many cases it's a sudden lifting with resultant full regen "braking" whilst in other cases it clearly is the application of the brakes very firmly indeed. It's a good idea that people posting should do their best to clarify which it is when describing incidents. Certainly the expression "pin my head to the windscreen" makes it very clear for me!!