That is weird. Jane Anderson who has DH recently verified that See’s is gluten free as of 10-2018. Not officially “gluten free” because that would mean that the product has been tested to be under 20 ppm or even certified. But in terms of ingredients, no gluten was used.
More about the company which is now owned by Warren Buffett.
“See’s is not gluten free certified, ...
Actually, it is offen not corn starch these days - it’s cellulose or potato starch. But, even if it were corn, corn is safe for Celiacs. The protein in corn is not the same as they proteins in wheat, rye or barley.
“Numerous studies have failed to detect any immunogenicity by prolamines outside of wheat, barley, and rye. Therefore, corn doesn’t contain gluten,”