Thanks for the update. I have a Google Pixel 2 running latest software update (Android 9.0 Pie). Spotify version is 18.104.22.1683 armV7 (the latest update available).
Here is my battery usage today. As you can see, the Spotify usage isn't *too* bad on it's own but it is triggering Google Play Services all the time it is on, effectively doubling the battery usage. There is no other app that does this and no valid reason I can think of for it to need to do this. For comparison purposes, on days where I don't use Spotify, my Google Play Services usage never goes above 1-2%.
More than happy to provide further information as required.
I am also running a Pixel 2 with Android 9, and my symptoms are just like those of the topic-starter. I have also deleted the app, cleared out the cache, and reinstalled the app, but the problem still remains.