How to make Swift Sneak obtainable by fishing in certain places (1.21)

I am making a skyblock pack, and I want to make it so that when you fish in a certain structure, you have a chance of getting a book with a random level of Swift Sneak as a reward. Right now it does successfully give you an enchanted book, but the book doesn't actually have a specific enchantment on it. I used Misode to generate the following, and the output window isn't giving me any errors.