Actually, I watched a playthrough of 3d, and while it's true Sora wouldn't get his Keyblade without Ven, that's not the reason he failed. After all, Yen Sid did say "You both deserve the honor". However, the reason why Riku was the only one that passed was because he made an extra trip into the world of dreams to save Sora.
See, this plot reveal made no sense either. In KHI, Sora conquered the darkness within himself in that the Keyblade chose him and not Riku. Then Riku magically becomes immune to the darkness between KHII and 3DS and suddenly the situation reverses? Eh. And, actually, Riku passed the exam because Yen Sid said he was the only one who dived into the darkness to save a friend, which is stupid too because Sora was never given that option; we all know he would have done it given he sacrificed his heart to save Kairi's, which is the main reason he's so susceptible to the darkness now. =/
Yen Sid said at the beginning that if they both woke all seven Sleeping Worlds, they'd pass the test. At the end, like a jackass teacher, he changed the qualifications. o3o
Rants aside, I adore this picture!! You draw the KH characters so well. I normally avoid chibis but I can't stop admiring your comics. They're just so adorable. <3
It was because Riku did an extra to save Sora, when they return from the realm of sleep Yen Sid gave Riku the honor because he was willing to save his friend Sora. So Sora had to finish where he left off. I'm sure he passed it eventually. Of course Sora deserve the honor, but the thing was he was kidnapped by the organization so he unable to pass. But luckily he was given another chance to finish.