It is totally true for the context of this conversation... Which is, software subscriptions.

No, you cannot use Stripe for software subscriptions. Stripe (non-Apple pay) can only be used for physical goods, or sale of services rendered outside of iOS/MacOS.

In other words, can only be used for non-digital sales. The context of this conversation is the Hey app, which is a software subscription, so no... there is no other way to pay.