The stock ECU adapts it's base tune using the stock narrow band sensor. This is intended to be a VERY crude way to compensate for the slight differences in each bike during manufacture and account for wear over time.
IT IS GARBAGE.
Basing any sort of adjustment on a narrow band sensor is absolutely terrible for power, mileage, really for everything except emissions.
Resetting the adaptives zeros out the fuel trims (which are hidden you can't see them). I think i did it one time, a few years ago, but have never done it since. I consider unnecessary, and, in fact, a few members have had issues with how their bikes ran after resetting adaptives when using known good tunes.
I consider it extraneous and totally unnecessary when using a PC-V or when you have the stock O2 sensor disabled.
I've loaded probably 50 different tunes and updated my own tunes probably 100 times in my ECU, all without adaptives reset, that is what I base it being "unnecessary" on.