Yes, we build apps for gym and personal training businesses. Most of the value is delivered in-person or Skype (assessment, workout design, taking client through a workout etc). I feel like the guideline is not clear cut.
The personal training business has a high marginal cost and unlike games or other digital services, the value can be unlocked immediately after in-app purchase.
I feel the marginal cost of a product should determine what qualifies for this guideline. But for now we are in limbo.
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."