BartK What they did instead was to take the recordings/piano rolls and using AI and/or other processing techniques re-created the sound that Cortot would have produced if he had modern recording technology. In other words, it's not an original recording.
The three Nocturnes at the beginning of that compilation are from 1952, certainly from the LP that Cortot recorded in 1951 at the Abbey Road studios. Recording techniques were already well advanced: if one of the original masters had been preserved, it would definitely be possible to produce a very clean remastered version. These pieces were remastered in 2017, so there's no AI involved.
The other pieces in the compilation come from 78s published between 1923 and 1935 (no piano rolls) and you can hear varying amounts of needle noise.
Noise reduction techniques may have taken away some of the higher harmonics, but apart from that, what we are hearing here is certainly very close to the original recorded sound.