He's a former Spotify employee now, but he was a Spotify employee when he made it. I think it hasn't been updated since he lost his data access.

I have a lot of respect for Glenn McDonald for spam fighting all these years on Spotify, but we can go better than PCA for mapping music these days. Any neural embedding model is going to produce more meaningful axes. In fact Spotify had an intern who did just that, just before the launch of Discover Weekly: Sander Dieleman. Along with Aäron van den Oord he was snapped up by Deepmind after their Spotify internship. Those two guys were (and are) wildly good at what they do.