Please refer to the attached project that reproduces the issue. In the MainPage constructor, you can switch between using the PickerEditor (validation works) and the SegmentedEditor (validation doesn't work).
// Works with validation
dataForm.RegisterEditor(
"Location"
, EditorType.PickerEditor);
// Doesn't work with validation
//dataForm.RegisterEditor("Location", EditorType.SegmentedEditor);
Nullable int property is validated against range when no data is input.