At airport locations with Rapid Return, the attendent always gets in and checks the mileage and fuel level before loading it into their portable terminals and handing me a receipt, so I've never had an issue of being charged for fuel.

At my local edition, I tell them I filled it and they never have charged me.

I've had two after-hours returns last week at my local edition. I note I filled the tank and both receipts did not have a fuel charge.

Still, I double-check my receipts now just to be sure none of the reported shennanigans happens.