They get supported with the purchase of the song, but I do not see where they get any analytic data showing how often that purchased song was played or additional royalties from playing the purchased song. They do get analytic data and royalties for how often it is streamed which is not the same as a play count for a purchased song that can be done offline without an Apple Music subscription.
The difference seems to be, are you playing the downloaded song from your Library, or are you streaming the song from the Apple Music platform where it is being streamed, and requires the subscription to Apple Music? For streaming royalties to be paid to the artist, you would need an Apple Music subscription.
Here is the analytic data that is used to measure that the artists sees.
https://artists.apple.com/support/1105-understand-your-analytics