According to the principles at Astoria, Parsons was not responsible for the "sound behind the original DSOTM" in any significant way. Further, when it came time for the remasters, Guthrie was the unanimous choice because he knew the project better-- inside and out. There as a tiff over that, of course.
According to the studio, the band played the lead role in assuring top sound quality for that particular masterwork, not the mastering engineers. The Studio felt Guthrie was the talent behind the panel, not Parsons, though Alan did get accolades and a lot of the credit.
Guthrie and Doug Sax still work together today and there is no love between those two and Parsons.