I only recall seeing and playing Invinco / Head On 2 cab and that was it. For the time I spent in arcades during the late 1970s, it seems like I would have seen more dual game units. I mainly saw single game units. The dual game unit was probably somewhat rare. The only good game was Head On 2 and that was it.
The company probably created the dual game concept just to unload all their crappy games inventory on unsuspecting vendors back then.