It's separate pots for ad listens vs. subscriber listens. AFAIK there are also separate pots by country, since subscription fees and profitability of ad markets vary widely by country.
Do you have a reference for this? If the pots are different, what's the practical difference, when the majority of the profits, and payout, comes from premium?
This is easy to check. Yes, premium listens are pooled separately from ad-supported listens.
If an artist is extremely popular with ad-supported listeners, that doesn't let them eat into the pool of payments from premium listeners.
Note, however, that listens are pooled by country, not per user. So premium accounts running background music in a hair salon 6 days a week will decide where your subscription money goes far more than the music you listen to.
Originally, this was because the big record companies demanded it. Now, the record companies are having second thoughts, but Spotify, which has adapted to the funding key favouring background music, are the ones resisting.
