Well "Rinoa is not Ultimecia" certainly doesnt leave much of an impact. Sounds more like a receptionists reply than anyone high up. To be honest, Who decides? Square and the FFVIII staff is a large group arent they? Who even said that statement? It sounds like they didnt give it much thought but it would certainly be a brilliant plot twist and would actually come close to making a character out of Ultimecia. I certainly like the theory.