Downloads.
The one you see are the numbers Apple share with you. Not real ones.
Damus had too many downloads and this make it visible on their radar.
Fountain not so many ..
The narative is "we support inovation, we make easy to devs to make and post ios apps".
Until it's small and insignificant they *let it be done*, what's the point on getting bad reputation if there is no risk to their monopoly?
Damus got too many downloads, it became a real risk.