Some microwaves have a humidity sensor that determines if the popcorn is done and it works well.
Some microwaves have a preset cooking schedule for microwave popcorn and it doesn’t work for all types.
Personally if I’m making microwave popcorn, I just set it to 99:99 and wait for the popping to stop.
Archangel1313@lemmy.ca 6 hours ago
I think it’s more that the popcorn maker can’t guarantee that you won’t burn their popcorn, or wind up with half a bag of un-popped kernels, by using your microwave’s internal settings. The warning is, “we take no responsibility for the outcome, if you press that button”.