Yes, I think they didn’t want to compress, so that the sound is ‘pristine’
Some of the sample sets were recorded in an anechoic chamber that the Speech & Hearing department built near the hospital. I’ve been inside it and it’s spooky! They use it for hearing research but anyone on campus can reserve time in it. My son did some voice work in the anechoic chamber when he was 10 years old for an educational CDRom, which is how I got to visit.
What I want most out of that anechoic chamber is the 1950s vintage Altec mono tube mixer that was just sitting in the corner!