They say that it's a licensing limitation... DTS will not license anything other than Bluray players and AVRs with DTS-HD MA.
So that means:
1) Everyone else is implementing it illegally.
2) WD Doesn't understand that no license should be needed for PASSTHROUGH, only for DECODE, and keeps asking for a license. Meaning their lawyers don't know what they're doing.
I think it's #2.
Yes, you do get the CORE 5.1 in DTS-HD MA tracks.