That's a new one. I've visited 4-barrel breweries and Widmer and breweries in between. I've never seen a brewery where they used the mash tun as the boil kettle. Not saying it doesn't happen, but I'm running about 20 out of 20 don't.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk