I've noticed there is a bug with the grouped list view when using the datasource. When the group is removed the listview reverts to ungrouped but the styling is not updated.
I discovered the fix below... but the framework should handle this automatically.
(Tasks is the DataSource Object)
The grouped listview looks fine. Until...
Group is removed but the list formatting does not revert to the appropriate style.
The following manual
updates need to happen:
Now it looks acceptable.