Every single strain on the planet has the potential to produce male flowers.
I feel that the fear of herms is overplayed and over exaggerated. It really isn't the end of the world. Of course it would suck to spend a few hundred on beans and have all of em herm, no doubt about that.
But I had some intersex traits in my Dank Zappa. In one male and one female. No biggie if you ask me.
Also I'd like to point out that many of us are more n00b than we think we are, and the stresses could have easily been brought on by us, the gardeners, even though it may not be apparent.