Relatively large amounts of deactivated yeast (brewers yeast) are routinely added to pet foods as a natural source of b vitamins and protein and I'm not aware of any problems emanating from its use. In this form, yeast can constitute up to 2 or 3 percent of the food's total weight while 10x the weight of the sodium selenite/selenate supplement would be tiny - around 0.000006% if my maths is right. Not a cause for concern in my book.
Selenium itself is not the problem. Some selenium is necessary for normal health and, unless the producer makes a concerted effort to ensure it is included in suitable amounts in the raw ingredients, it must be added as a supplement. Both sodium selenate and sodium selenite are classified by the EU as toxic (very toxic in the case of selinite) while selenomethionine, the compound found in selenium yeast and throughout nature, is not. Selenium yeast has long been known as the best natural source of selenium for both humans and pets. All of this information is widely available across the internet and I know which one I would prefer to feed.
As for not wanting to 'bite the hand that feeds', I can assure you that I would be a lot better off if I were that way inclined. The site exists only to provide, to the best of my ability, the truth about pet food, warts and all.