Yes, that uses the non-public API for smart speakers and the likes. If and how Spotify can crack down on this is not well known at this point, but here's hoping they're using API keys from an old but popular device that's no longer receiving updates.

My raspotify/librespot install stopped working last week until i blocked apresolve.spotify.com on my network.

It seems they are switching some regions to a CDN that is not supported by librespot. There is some discussion on the librespot issues github page (https://github.com/librespot-org/librespot/issues/972)