I was told something slightly different. I am allowed to drink any protein shake as long as it has at least 20g of protein and less than 15g of carbs. I currently use a powder that has 30g protein and 3g carbs. My favorite drink is a "frappuccino" that I make using a very light decaf coffee, a little oat milk, two scoops (1 serving) of vanilla creme protein power, and a few ice cubes. I blend it together and it makes an incredible drink that reminds me of Starbucks but is very low in carbs and high in protein. It's my favorite.
I just realized that RNY and VSG may vary slightly in the post op diet, I'm not sure what you had. I had a VSG on July 16th.