Btw, for anyone interested: stretching like this is typically done using the PaulStretch algorithm, invented by Paul Nasca. I'm not familiar with its workings, but would guess that it takes granular samples of the track and replays those: the sound is sorta similar to what granular synthesis produces. (Edit: looks like it also applies FFT and does some mathematical trickery.)
The algo was popular back in the vaporwave days for extreme slowing-down of popular music. It's currently available in Audacity out of the box.