Why is it a bad idea for MasterDetailPage to use the Toolbar?

At first, I thought this is a bug:
http://forums.xamarin.com/discussion/54575/problem-with-formsappcompatactivity-and-masterdetailpage#latest

but it seems like it's done intentionally.

I checked the sample provided by Xamarin.Forms guy:
https://github.com/jamesmontemagno/Hanselman.Forms

And I can see that the same thing is happening there:

As you can see, the drawer is hiding the toolbar, that's because the MasterDetailPage doesn't use the Toolbar at all despite it being the MainPage. The Toolbar is attached to the child Detail page inside MasterDetailPage.

This new behaviour only happened with the introduction of FormsAppCompatActivity. Why is that?

Cheers,
Space Monkey