An overbanked turn isn't designed to turn the rider upside down, whereas an inversion is. An overbanked turn is designed to make a direction change smoother and more comfortable at higher speeds, and conveniently makes the ride a bit more thrilling at the same time! So no, it isn't.
With the Stengel Dive, it doesn't really fit the bill of what I said above, as it is really a unique element just to thrill, but its basically just an overbank on the top of an airtime hill. There's overbanks that bank more than that though, so I wouldn't say that's an inversion either.