I wasn't clear in my question. Richard's post said that "F-22 type 2D nozzle is supposed to be stealthier while a quasi 2D nozzle made out of a 3D nozzle is not". Therefor I asked why use that quasi 2D nozzle, I did not mean the F-22 type 2D nozzle.I believe he was referring to the axisymmetric nozzle.
Axisymmetric nozzles are circular nozzles. 2D thrust vectoring nozzles are the ones used on the F-22.
I might have misinterpreted your comment, but I believe 3D thrust vectoring could have negative effects on the stealth characteristics of the aircraft. I’m not entirely sure.