That’s a fair point, but isn’t their evidence to suggest Corrin began work 8 months prior to their release?
Here’s the actual quote from Sakurai
“The process, however, of actually creating a character often takes well over a year, where we are constantly working on the model, the animations, the audio and the balancing. For the game balance we have a testing team playing almost every day and we make adjustments based on their results. I was working from morning to night with my responsibilities as director, so I was only able to spend Wednesday evenings and weekends on the balance.”
This seems to suggest that ignoring everything else characters still take over a year to make. Even if the game is done, I can’t imagine the time to make a character is considerably shortened. 8 months seems like a reasonable assumption. Especiallly since their won’t be as many people working on the game post-launch, which would only further enhance the time taken to develop a character. Either way, it would imply Mewtwo began creation prior to the game. You also have to consider that a character at TGA would likely be third-party, so negotiations would take place months prior to the game releasing.