The idea that high glycemic index foods are bad for you is misleading. It's only actuate if you eat that food exclusively. As soon as you eat something else, especially fibre, your digestion slows down and the measure is meaningless. A single ingredient with high GI doesn't have any indication of the overall healthiness of the milk.

There's no trans fat in oat milk.

They misread the research for dipotassium phosphate. It can be harmful for people who already have damaged kidneys. It's considered safe by the FDA and commonly added to dairy products, such as regular milk.