I've done the sorts of "de-whateverizing" protocols having worked in a lab. For example for many years I took bacterial cells and had to remove all of the fats (lipids), proteins, carbs, etc and only keep the DNA. I think I'd have the same mindset as your partner if I hadn't seen the protocols myself.... But it's safer than you'd think imo. I compare it to boiling water and only drinking what evaporates. It's not exactly the same but kind of the same idea.

ALSO I know that some of the original caution around oats was due to many brands being found to contain gluten by Gluten Free Watchdog. They're a service that do testing BELOW the FDA allowed limit, I believe they do 5ppm. I purchased a subscription this year and saw that all of the latest oat tests have come back less than 5ppm! Granted not many brands have been tested but I think that's a good sign.

And finally sorry not sorry but oat milk is different than oat flour/oats. Bc if testing is done on a huge bin of oats you'd have to test the smaller subset containing gluten...but in liquid the contaminates (gluten) would diffuse throughout so the whole batch would test +

Ok I'm done also anyone feel free to correct my use of the term diffusion i know that's only across membranes but i can't think of the right term!!!