yoda-sama said:

Did the canonical status of the original Clone Wars series officially get stripped? If so, did it go out the window with the Expanded Universe, or sometime before that (in short, explain this canon purge)? Also, does the CG Clone Wars series ever deal with the events directly leading up to Episode III?

Sadly the 2003 Clone Wars series is "Legends", at least as of now. Which sucks, because the two fit together ok.

The closest the CGI series got to EP3 was an arc with Yoda about learning to be a Force Ghost and an arc about Order 66.