Now, this is pure speculation on my part (from some experience as my wife and I both own 2021 Honda vehicles currently, and I previously had a 2017 Honda with the system, as well as my wife's last car having a similar system, but not being a Honda), but I wonder if the issue is not a malfunction, but partly the owner/operators fault.
The only reason I say this is that the sensors for the system (it is a camera in the rearview mirror paired with radar located behind the Honda badge in the grill to the best of my knowledge based on Honda's info on the system) are easily confused by uncleared snow. I live in Northern WI, and on days in which I was lazy about completely clearing snow/ice from the upper windshield and/or grill, it can activate, but was resolved by clearing this snow. Hypothetically, if I failed to adequately brush snow off the roof (we have all done it) and the snow slides off the roof and onto the windshield during a braking or other maneuver (again, been there more than once), I could see a situation of the system unexpectedly activating (in its mind, the sudden obstruction of a sensor could be an imminent problem) for "no apparent reason" if you didn't know about the sensors' locations and how they operate. After you get rear-ended due to such a hypothetical situation, would you really take the time to go: "hmm right as that happened a small amount of snow slid down the windshield"? Probably not.
Now, a few weeks back in my work parking lot, I was pulling into a space, and my braking did cause snow to slide down the windshield, and the avoidance did kick in, so I have in fact experienced such a situation in my 2021. A contributing factor in this case was that, since I was pulling into a parking space with a vehicle in the space in front of me, the radar was sensing a close object (within 3-4 feet) at the exact moment the camera was obscured.
Now, I certainly think that if my theory is the case, then Honda should consider re-programming the system to ignore brief obstruction of a single one of the 2 sensors to mitigate the situation (or add a 3rd sensor or make the sensors able to "see" through snow if such a thing is possible), but again is it a flaw in the system, or operator error, or both? Although 278 occurrences is alarming, but considering this is only 0.016% of the 1.7 million vehicles recalled, and they are likely driven daily multiple times (let's say for argument's sake the vehicles are driven 3x daily on average and are 3-5 years old for the amount of trips that accounts for) we are talking 278 occurrences over around 7.5 billion drives. That is not a statistically significant amount occurrences.