I read this as splitting each user's monthly payment only across the artists they themselves listened to (like how YouTube premium works) instead of pooling everything together. So artists with more paying listeners would get more, while artists who only get listened to by free bot accounts wouldn't get anything.
Do you mean, how do you handle $0.001 monthly payouts? Spotify could set a payout threshold. If the threshold is not passed in a given month, the balance carries over to the next month.