I've looked into this, but haven't yet found an obvious way to enforce purity mode on that level. CarPlay, remote controls like for AirPods, or the Now Playing controls in Control Center go straight from the OS to the underlying music player without a way to customise this behaviour.

I'll check if I can detect "premature" track changes, intercept them and then switch to the next album. So rather than doing this on the level of pressing the button (as its done in the app), it would take the signal of a track change, and then check if you've violated your purity setting.