MMS is not an antifungal. It is an inorganic compound, an oxidizer.
Yeasts have statistically no chance to develop resistance to it because it acts and the molecular level and very, very fast.
Of course, evolution may render some new yeast species with some kind of resistance, but I doubt we can call it yeast then. Yeasts make their chemical environments acidic, it's kind of their fingerprint. Miracle-Mineral-Supplement on that environment will rip the yeasts from their antioxidant buffer mechanisms at the micro-cellular level, hence killing them.