I actually tried this the other day with my new Bosch wall oven microwave. It appeared to block the signals enough to prevent my phone from receiving calls, which is what I would have expected from any microwave. I figured a microwave is probably the best Faraday cage that people have sitting right in their house.

I'm surprised that the phone in the video was able to receive a signal.

I wonder how much 2.4 GHz power is leaking from that thing.

A microwave with a bad shield has the potential to leak a ton of power at a frequency that's used by many devices.