The nutrition part of that is a separate issue. FDA recommends that a product calling itself oat milk and having a materially different nutrient profile from dairy milk voluntarily identify relevant nutritional differences
But they still have to say OAT MILK or SOY MILK. They are just allowed to use the term MILK itself after. Otherwise it would be "OAT MILK-LIKE PRODUCT" or something similarly stupid.
This is just saying they can call SOY MILK that, not that they can pass it off as MILK with ingredients: Soy...