Is what true?
I have no reason to know whether or not they are lying, but I certainly assume they are right about their product. WMV HD content is currently available in HD form. There was a DVD player that was capable of playing WMV HD material, but I do not think it is available in the US. In any case, yes WMV HD provides native HD source material, and most everyone using WMV HD material is using an HTPC.
No you cannot play WMV HD material in any way on a normal DVD player. Most movies that contain WMV HD versions have them on a second disc. The first disc is the regular DVD format the second DVD disc contains the WM files.
For more info:
http://www.wmvhd.com/