After delving further into Hi-Yield Spreader Sticker in order to answer the question I've come to the conclusion that it shouldn't be used. It consists of alcohol ethoxylate and alkylphenol ethoxylate. Alcohol ethoxylate appears to be surfactant only while alkylphenol ethoxylate does have emulsifying properties. Alcohol ethoxylate appears to be safe, however alkylphenol ethoxylate is an xenoestrogen (it acts as an estrogen). It's been proven to cause the feminization of aquatic organisms and decrease male fertility in those organisms. There are predictions that most men in North America, Europe, Australia, and New Zealand will be infertile by 2060 and I have to wonder if ths is a contributing factor.
Bonide brand spreader/sticker, which contains the same ingredients, is listed as "not for sale in California". Of course, that could just be because they refuse to pay the fees California demands for certification.
Southern Ag spreader/sticker contains octyl phenol polyethoxy ethanol, a known carcinogen, and also contains isopropanol, rubbing alcohol. Monterey "spray helper" is mostly cotton seed oil but also contains the above mentioned xenoestrogen, at 17%, and isopropanol.
I could find little to suggest that Tween 20 (Polysorbate 20), suggested by Millet, is harmful. Polysorbate 20 and Polysorbate 80 are the same base chemocal, polyethoxylated sorbitan. The difference being lauric acid.added to Polysorbate 20, and oleic acid added to Polysorbate 80. Polysorbate 80 is not known to be carcinogenic, but studies have found decrease fertility in rats at very high rates of ingestion. The key being "very high rates". So, Tween 20 appears to be the safest option.