Joe,
Another thing is that they wouldn't have had to put the phones in a ring around the corn if this was true. Since in this instance there was nothing to control or aim the microwaves, they would have done the same thing if it was true if the phones had been laying anywhere near the popcorn. And in an oven the microwaves are in a closed environment.
Now if they had done this standing in front of a high power microwave antenna that was transmitting, it would have been believable. However they wouldn't be around to talk about it.
Ron