I'm no chemist, but the amount of starsan that is usually involved, is minute. And, even if there were a more significant amount, you'd have to understand exactly how the yeast were metabolising the starsan, and what the resultant outgassing is, to know how it affects the beer.
From all accounts, a small amount of starsan is indistinguishable as far as flavor is concerned. But, I believe someone must have found out that yeast can actually consume the starsan, and they likely know the chemical makeup of the stuff, so that is where they draw the conclusion that it is safe to drink or brew with.