The Sonar X3 Explained were never intended to be specifically about the new features. It's a series designed to get users up and running from the ground up, which of course includes the X3 intended workflows; some of which are new to X3.
The new series is only about the new features. There's very minor overlap. For example I covered region FX and Melodyne in the Explained series. I covered it again (with completely fresh videos) in the new series. I'd say about 90% of the content is material not covered in the Explained series.
You can see a detailed description of exactly what's covered here:
http://www.groove3.com/str/SONAR-X3-New-Features.html?action=print Eli