There is precedent. There were CGs of J-20 floating around internet before the first close up photo of J20 showed up in this forum. Those CGs were very accurate. Just someone who live in XAC complex memorizing what he/she saw and do a good CG work would be enough.how can you tell a CG rendering of an original that has not yet been clearly seen is accurate?
P.S. I am confirming this particular CG but only saying it should not be dismissed as easily as trusted.