There's always going to be "marketing speak" in a competitive environment.
PCH never said it was the only one capable. All it claims is it was the first to support the Matroska 3D specifications;
You can read about it;
http://www.matroska.org/news/popcorn-3d.htmlAs for full 3D, again another claim made by a marketing team. If you want to get technical about it, full 3D can mean display 2 streams using SBS or TAB because even 720p is HD as long as it's not Standard Definition (SD).
What's special is that it implements Matroska 3D standards so it doesn't require users to shift from 2D viewing mode to 3D when it encounters a Matroska 3D encoded file.