Be sure to listen with your ears, not your eyes
. But seriously, yes, it is true that these Glass Hammer files originated at single sample rate.
When I mastered them, prior to mastering, first I upsampled them to 32 bit float at 96 kHz, using the world's best sample rate converter: the Weiss Saracon. All my processors, analog and digital, perform better measurably and sonically at the higher sample rate. You can read my book, "Mastering Audio: The Art and the Science", for a technical explanation why the processing performs better at the double sample rate.
After mastering with both analog and digital processors at 96 kHz, I then went two more generations in order to produce the Glass Hammer standard rate CD: First I downsampled to 32-bit float/44.1 kHz. Then I dithered to 16 bit at 44.1 kHz. The result sounds smaller and a bit harsher than the original 96 kHz master.
In addition, most chip-based D to A converters perform better at the higher sample rate as well. This is also explained in my book.
So, by playing the 96 kHz/24 bit files you are getting the benefit of the warmer, wider, purer reproduction of my original masters. Granted, there is no high frequency material above the original Nyquist frequency of Glass Hammer's original files, but it is very debatable whether the ears can detect or get any benefit from those additional high frequencies. In fact, the debate continues on whether 96 kHz files sound better because of the increased bandwidth or the better filtering!
Bottom line: It sounds better, it is better. If Glass Hammer recorded and mixed their original files at 96 kHz, there might be additional information above 22.05 khz, or there might not, depending on the original instruments. The live drums and cymbals would exhibit additional harmonics. But whether you can hear them is debatable, although I am very convinced that recording and reproducing them at 96 kHz sample rate sounds better. We just are not sure why, and looking at an FFT is a pretty deceiving situation because our brains are very quickly fooled by my eyes. Until we can do a like-for-like blind test with single variables, that part of the mystery will remain. I can assure you that you are getting the benefit of listening to a greatly improved and earlier-generation master compared to the master used for the compact disc. Use your ears and report back and tell us if you agree on the sonics.
Lastly, I want to point out that Glass Hammer is selling these 96 k files at a reasonable price, largely because they did not originate at the 96 kHz rate, so that folks like you with FFT measuring gear won't complain, and will hopefully use your ears and also learn the provenance from the mastering engineer.