Ok, well I would guess the two groove model would be the updated version given that mine being over 20 years old has three.
It's possible yours slipped through the cracks missing two spring clips, but hey, things like that happen, and Park is really good about making it right.
I recently upgraded to a newer model truing stand that was supposed to include thru axle adapters. I bought it through an authorized wholesale distributor and it came in an undisturbed box with all staples in place, but the adapters were missing.
I contacted Park directly rather than going through the distributor as the box had obviously not been opened after leaving the factory, and they promptly sent the missing parts.
Not the first time they made something right for me.