If Kate and William didn't want their son to attend Eton then there was no reason for him to sit the various recent tests
Just wanted to point out that there is only one exam (ISEB pretest) across all 13+ day/boarding schools now. You sit this online exam once and the score is sent to all the schools you have picked and paid for. Parents can't see the score. The callbacks for the high scorers come in mid December for the interviews. Which means George has already cleared the first round of the process involving the pretest scores and reference letters.
Most schools have scrapped the common entrance exam now and only do interviews, except Eton and I think, City of London.
DS went through this process and we found Eton very accommodating and trying hard to be egalitarian. But the adjective Etonian is still problematic so we decided not to take the place, same with Wellington. Several boys in DS' year had Eton offers - I wouldn't call any of them super intelligent, but smart, mature, polite, passionate about one core field and with a wide range of interests. Intelligence or ISEB score is not the only criterion for admissions even for the common man (riff raff like us!).
Wellington is a good shout. Quite a few royals still studying at Wellington. I think Prince Albert's son recently graduated.