Right now they only have tooltips and causes wrong announcement order. See b/234580483.
The native Android pronounce 'Back, button, double tap to activate'
The Flutter pronounce 'button, Back, double tap to activate'

If we do add labels to those buttons, we should make sure the announcement matches the native Android.

This is also blocking internal customer to write integration test that relies on semantics label to locate the backbutton
b/237459242