Well, he was straight forward about the situation in the interview he gave, and stated that often HDTracks does not receive information from the record labels regarding the process of mastering the hi-res versions. To be fair, several recordings do give detailed info, for instance one Stevie Wonder album was remastered from original tapes... But on the whole, very little info is given, and frequency analyses of many tracks that I've seen posted show sharp filters cutting off at 22khz.
Even so, I think HDTracks should post "mastering source unavailable" or as much info as they do have. I certainly wouldn't want to pay for upsampling that most of my music players could do on their own.