Mine just "forgets" that i have songs downloaded over time until i go online, so my playlist will effectively gradually shrink. And then as soon as i go online they're instantly available and downloaded again...

Google Sheets does the same shit. I downloaded a sheet I use from my phone for work because my workplace has shit data connection and no reliable wifi... Yet it still takes ages to load because it refuses to use the downloaded copy.

And I'm too obstinate to turn off my data, lest my podcast stop playing, leaving me alone with my thoughts u_u

I think if you have any internet connection at all spotify still tries to phone home when you play a song to add it to your algorithm and ad data