@yogthos MVVM stands for Model-View-ViewModel, and is a pattern commonly used in dotnet and winui apps for decoupling backend business logic from frontend UI.
For example, this: https://youtu.be/Nb6fEeYfDAU
I feel like I'm the one being trolled here.
What on earth do you mean by "no app provides APIs to access the business logic layer outside the UI?" These apps are using APIs to begin with, the app doesn't NEED to provide them. The devs provides them to the app, the other way around.