HaLeiVi -“Health, I don’t think the Bracha comes from the Rav Hamachshir. I’ve heard of many such instances where the Rav was contacted and said that the Bracha, or some other non-Kashrus Halachik fact, was not his doing.”
Oh and it’s just a coincidence that all the different restaurants tell you the hamburger rolls etc. are Mezonos. And you see from OC:168 SK: 24 that even eating the Mezonos roll with meat you only have to wash & make Hamotzay if you become full from the amt. that you’re eating.