I wasn't aware that Spotify had some sort of "smart" normalization going on but my point still stands. Normalization can only reduce audio quality by reducing dynamic range, not enhance quality, so there's little reason to use it if you have a functioning volume control.

I could also go on a tangent about how using normalization at a low volume level (which is essentially the same as reducing the volume in the Spotify app) is worse than keeping Spotify volume at max and controlling the volume via the OS mixer or an analog knob, but that's beside the point.