Gross over-simplification. For anyone curious they have videos out there, though they are 10+ years old now so may no longer be accurate, but in 2019-era this was still a thing (company I worked for did it too).[1]
(I was active as a coach in Stockholm around this period and know multiple people, both engineers and coaches, who worked at Spotify including Henrik the author of the video.)
This is why all the sections of Amazon.com are barely coherent. AWS does this too but it’s more naturally split and text works better than stateful rich media.
The headache of using the shared playlist "Jam" feature and trying to add a song without playing it directly. There is like a separate queue system for "Jam" and things work differently.