They only way it can ask for root permission is if YOU selected to give it root permission the very first time you launched the app. That allowed magisk to add it to it's list of root apps that would then, after manager update, would ask again for root access.Same here..the latest Vanced manager 2.5.0(weed) asks for root permission.
I'm using non root version tho..
The app hasn't changed. Your setup and the way you initially set up vanced manger is why it asks for root.