No it doesn't, Spotify provides line-level accounting for every stream to the rightsholders. What they then do to account to artists could be anything.
Doesn't matter. Do they provide line-level accounting for ad revenue? Do you know what percentage of TOTAL revenue gets paid to artists?
No because Spotify pay the rightsholders who may or may not be the artist.
You're missing the point. Let's say Spotify pays rightholders 20% of gross revenue for streaming. Then they take another 40% of the gross revenue and pay the major labels for advertising, marketing... whatever. That's hollywood accounting-- it's not streaming revenue so they don't have to report it. Ever notice the labels don't complain that the streaming rates are so notoriously low? Why don't BMG/UMG/WMG just band together and demand an increase in streaming revenue? Because they WANT to keep it low so they make the real money on non-streaming revenue that doesn't go to rightsholders. Maintaining control is the issue and that's why they forced Spotify to make people work through their "partners"