So it was my understanding that G80 was limited slip or posi or whatever
You wanna call it when BOTH rear tires are your drive tires.

So I assumed that I had a single rear wheel as my drive tire but today
While driving out of my garage with a slick floor plus rain soaked tires
I ended up spinning the tires getting over my flood control 2x6 that keeps
Water out of the garage. So I get out and notice oh crap! There are 2 sets
Of skidmarks! So I do have both rear wheels as my drive tires even though
I do not have the G80 rpo code? Or am I mistaken about only 1 wheel
Being the drive tire?

 

Well, there's a saying "given enough thrust, even a brick will fly." Unless there's an appreciable imbalance in traction, both wheels will break loose even with a standard differential given enough torque on the driveshaft. One way to find out for sure is to lift the rear and then try turning one wheel with the transmission in park (driveshaft locked).