Popcorn presets either detect steam once the popcorn is almost done popping (then runs for N more seconds), or actually use a microphone to detect the time between pops (I think the latter is more accurate). If done well, it can work well. Apparently it’s often not done well because the bags of microwave popcorn almost always say “don’t use popcorn setting!”
The problematic popcorn settings are the ones that don't have any such detection and instead ask you to enter a weight and they choose an amount of time based on that. It's very inaccurate and causes either many unpopped kernels or some burning.
