You are right. Under Win XP my Notepad does not have gradient background, but under Win 7 my Notepad has a gradient background with my Luna theme.With your Luna theme on Windows 7, you probably have the default system menu in 32-bit TC all the time (I assume that drawing own gradient is active only on XP). But the difference here is how default menu looks like. Again, check Notepad. Here the gradient is by default. So native menu in TC means menu with gradient.
Thanks for clarification - a pity though that I cannot disable it under Win 7 - I hate that gradient.