I fear that you misunderstand the question. Let me expand on it a bit...
The following is a direct quote from this MSDN page
about Themes and the .skin file ...
I know that some properties of RadControls can be set in the .skin file of a Theme so, given the above from MSDN, it seems fair to assume that some
properties of the controls have the ThemeableAttribute Attribute set, doesn't it?
Or are you suggesting that the MSDN documentation is wrong and that I can use a .skin file to set any