Since it is not impossible - even from a Hydrogen Audio viewpoint - that someone accidentally screwed up something in the code that affected sound quality, the bug report was reasonable - even if false.
It turned out to be a simple matter to go back and forth between 74 and 84, playing a DXD (24/352.
free test track from:
http://www.2l.no/hires/and I can confirm that there is no sound quality loss between 74 and 84.