I build the test sample and check it again, it looks my previous reply is not exact.
If you don't set custom zoomlevels, the map won't throw exception when you zoom into deeper, and it will strech the map.
But if you set custom zoomlevel to deeper, you will get the exception there it should make your application get crash.
The Android is based on Xamarin, and some feature is not implemented just the same like WPF edition.
And in Android edition, the Overlay+BingLayer is slower than BingOverlay, that's because they are in fact follow different tile matrix by default, the first solution get more calculation.
Here is the simplest code, you can see when you zoom in, the exception is not thrown and the tile map get stretch.
protected override void OnCreate(Bundle bundle)
MapView mapView = FindViewById<MapView>(Resource.Id.MapView);
mapView.MapUnit = GeographyUnit.Meter;
mapView.CurrentExtent = new RectangleShape(-11243423.7023786, 4768592.21409415, -11243022.114298, 4768003.21824261);
BingMapsOverlay bing = new BingMapsOverlay("your key");