You corrected me with another fans guess. It clearly states in that link "It says these pages are "based on training data supervised by Toriyama", though just exactly what this means is unclear" showing that, you have not corrected anything. All you have done is shown another persons interpretation of what happened.
i dunno guys .... both arguments are completely retarded .... how can u automatically assume that Vegeta couldn't go SSJ2 before ... heck in the manga we have no proof that Goku could go SSJ2 before he came to earth either .... ur not using correct logic here mcdaddy. besides i think vegeta would b able to master SSJ2 after the Cell games. he would have some kind of anger tiff with his pride about Gohan being SSJ2 and he would eventually become SSJ2. the only reason why Vegeta went majin was because he knew that even as SSJ2 Kakarot still had more power. he was able to kill yakon with his ki alone and still have more than enough in his reserve. obviously this was because Goku had the SSJ3 potential Vegeta didn't know about. Vegeta is a talented warrior .... he can size up a warrior pretty easily. even though he didnt know Goku could go SSj3 .... he still knew he was a lot more powerful than Vegeta was himself, even if they both did master SSJ2.
and in the dialogue it seems clear that Vegeta KNEW he could go SSJ2 before he powered up for it.