I've wondered if the specific vaginal flora has properties capable of fermenting dairy products into something like yogurt and I guess I now have my answer.
Whats the big deal anyway? The amount of bacteria needed to ferment milk into yogurt is actually quite small. When I make homemade yogurt, I innoculate milk by introducing some of older already made yogurt containing active bacteria and stirring it in. One gallon maybe needs 1-2 tablespoons to kickstart the process. Im sure in commercial yogurt making, the amount needed is less; I just give it a healthy dose to make sure as my kitchen is not nearly as regimented as a commercial kitchen or lab.
You guys (and lesbians) are ingesting way more of these vaginal secretions (and bacteria) during cunnilingus.