That's incorrect.
I believe, though I may be mistaken, that the initial upload process details this but I would need to look at the theme site source and/or create a dummy theme to check this, anyway...all one needs to do is upload the theme with the exact same credentials (theme name, email address, and author - if I recall), and it will be replaced with the updated version.
I would still be wary about the possibility of copyright infringement notices, though.
[Saint]