I can't find the article right now, but I read a while ago that the Spotify client applications are modularized, such that different feature teams can push updates to their individual feature without breaking or being interdependent on other parts of the clients releasing in sync. I'm not sure what the mercury database is used for or if it's maintained by one of those "feature teams" or is part of the core lib, but that lack of central oversight (and responsibility) could be one reason why such an easy fix isn't so easy to get fixed.