My F150 extra cab had 4 doors, but not like a regular F150 4 door pickup.

The two rear doors could only open once you opened the front doors (though they did have separate latches - just not on the outside.

I thunk a Mazda RX8 was the same way. The small rear door could only be opened if the front door was opened first.

Car manufacturers were not allowed to call them doors from what I have read.