The addiction docs here are very strict about the dosage and amount of benzos used for detox and would NOT prescribe for long term use for the risk of future abuse. They include xanax as a substance to be detoxed from, even if its being taken as prescribed.
Maybe it's a case by case basis? Idk, but I would listen to your doc over your sponsor. And even if you get a second opinion and a new doctor recommends a diff medication for your anxiety, I'd still get a new sponsor if it were me.