So if I'm understanding this right, you sell "app as a service" to personal trainers who then direct their clients to download the app you made them and track workouts.

I think the "digital service" is the app itself because you only get access to the app if you're paying for a personal trainer. So I guess they want you to support buying the app directly not as part of a personal trainer package even though I'm guessing nobody would actually do that.

It definitely seems like you're running up against the rule meant to prevent "buy a coffee and get in-game coins free as as way to get around the 30% cut."