Just another old welders tale. Just as everyone now thinks tig is the only thing, when Mig was new and mysterious It had all kinds of lore that came along with it. The not as good was just one of the tales.
For myself, I still use my stick welder often and the mig for most everything else. I dont use Enough moly to justify buying a Tig. When I do use moly, guess what. Out comes the OA It is faster than a Tig and I think does nicer welds. One thing it has over Tig is preheat takes care of itself.