Yes -- there was a time when DTS-HD referred to a totally different codec. I remember that. Today, according to this source I mentioned, Master Audio is lumped together with "DTS-HD" and shown as such on the AVR displays. It's confusing, to be sure, but he told me that it was a decision DTS made and ultimately implemented it in firmware updates for receiver brands. So, now, when you view a film that contains a DTS Master Audio soundtrack, the front of the AVR just reads "DTS-HD."
I hate it, too.
However, I did notice, when I looked at pics of Treb's Onkyo front display he provided, that apparently some brands are still using "MSTR" at the end of the reference -- perhaps the pics Treb took were before the Onkyo did a firmware update...I don't know. But I was assured that there was some kind of changelog made to DTS' decoding algorithm wherein Master Audio soundtracks only show as "DTS-HD."
I can share his PM to me about this, from another forum, if you'd like.