UPDATE
I had only been testing on iOS emulator, which remains the same.
On Android emulator I found the bindings to be working but SfDataGrid redrawing incorrectly from time to time, sometimes expanding the grid using horizontal scroll and other times mixing columns.
I added HorizontalOptions="FillAndExpand" and VerticalOptions="FillAndExpand" to the SfDataGrid which improved redraw on Android devices only, removing the horizontal scroll problem but sometimes a column is not drawn even though it's header is shown.
To summarize:
On Android devices work but intermittently a column is not drawn.
On Android emulators bindings work but grid redrawing has problems.
On iOS emulators bindings won't redraw the grid.
On iOS devices bindings won't redraw the grid.