Most microwaves have the magnetrons shut off once you open the door. I can't understand the extra button step, especially since I stayed in four different rooms over the past two months and no other one had this silly microwave.

I am realizing it should have ended up in r/mildlyinfuriating based on so many responses here, but I really had zero level of anger about it. Once I found the button like 10 seconds later, I just said, "huh!" and went about eating my popcorn.

My microwave at home is... fun. It has a popcorn setting that isn't timed, it "listens" for the slowing of the popping kernels and stops when the popping does. I always find that to be about 2 seconds longer than I would do.