from my understanding, this disc called HDAD, contains on one side a DVD-Video resolution, 96/24 and on the other side a DVD-A i.e 192/24 resolution. So the disc on one side can be played in your regular DVD player and the other in a special DVD-A player. However I guess both formats are coded in LPCM.
Also one more disc is included which they say is a regular 44/16 CD which has not been downsampled from the DVD-A/V disc but recorded simultaneously.
I think the comparison might be interesting between these disc, to see if this HF/LF trouble that you assign to Hi-res is available here.
Caveat is that this comparison is conditioned on none of them being "raw" files so it might be a moot comparison.
Do I understand you correctly that when you speak about the CD being much worse than the raw file you mean the CD is PCM format or do you mean the wav wrapped PCM?
PS. The Tchaikovsky is also available but not with 44/16 included and I ordered both Tchaikovsky and Sibelius, however I dont find the EVEREST disc so cant compare to it.