Now I checked it again, and it indeed works as expected, so I'm not sure why I was seeing the described behaviour before. The app did update in the last week, so maybe the developer fixed it.
Also, it wouldn't surprise me that this is the feature of Android Auto, and Poweramp simply provides the API to access albums, artists, songs and so on. That being said, I also did upgrade Android Auto to latest version few days ago.
Anyways, if it happens again, I will report it and maybe record a video.