(details: I was full-time tethering while plugged in. I assume the charge controller thought the battery was charging but it was actually slowly discharging)
Getting said info to the right place so next version's charge controller is fixed would be nigh impossible, but dropping the info in lots of high-exposure places might be a start.
I can only surmise what actually happened. I was full-time wifi tethering for a month or two and the symptoms along the way seemed to point to this cause. The phone eventually stopped taking power at all, until I plugged it into a USB port instead of the OEM 1A charger. At which point I realized the higher current was the problem, and investigated the cable.
It actually felt like a really nice cable - very robust and strain-reliefy. But apparently that's because the whole thing was mostly plastic and essentially headphone wires. Lesson learned!
If my theory is correct , it's a pretty stupid design. But I feel like there's probably many weird corner cases in consumer electronics that don't matter because 99% of people won't find them, and the ones that do won't realize it's a bug, and by the time anybody could put it together that specific model has been obsoleted anyway.