Not related to Spotify, but managing http2 connections is much easier with async code than with sync, and http3 will be much the same. You can of course probably spawn a thread that handles these connections and use channels, but it's not going to be particularly pleasant to work with.
With the Spotify API before I have wanted to do concurrent API calls. One api call gives you a list of song IDs in a playlist, then you want to get all the song info for each ID. HTTP2 multiplexing would be much nicer than spawning 100 different http1 connections