I've never seen the outer rings either. Only the middle and inner. That's not to say they dont exist just never seen them personally even when I was working in shops around the sort of time Onza stuff was big.
I’ve also never seen Outers. Onza listed the aforementioned Titanium cranks in those catalogues back then, but they never even made it into production. I believe it is the same with the outer chainrings. It would be cool to be proven wrong though…