Avoiding the code-behind file should mostly be aimed at by people following MVVM. My view is this: having business logic in code behind leaves your View and ViewModel dependent on each other (directly or indirectly).
If you restrict code-behind logic to behavior of the view itself only, then you can interact fully with your application via the ViewModels. This also implies that if you manage somehow to put business logic in the xaml itself (not delegated back to the ViewModel), this is also wrong.
To answer the question more directly: I see "do everything in XAML" as bind everything to your ViewModel / all business logic in the ViewModel.
