I’ve just been on a decent drive in both EV and Auto (which was mostly EV) and deliberately let the battery run out so that I could then see what it was like on petrol only.
To clarify, the battery won’t deplete below 12% and will switch and drive as a full hybrid. HEV mode uses more of the engine but, still prodominately drives as a hybrid. Sport mode uses full power combining both engine and battery but, will hop into electric if cruising every now and again.