Untrue. They only take a piece of IAP, which is standard business practice.

As an example, if you want the easy way to sign up for a VPN with an easy to follow subscription so you know when payments are due and on what date, purchase the plan via an IAP, but be prepared to pay a convenience fee.

Or, you could go to the VPN website and purchase it directly. It’s a few more inconvenient and you have to keep track of that subscription independently, but you don’t have to pay Apple anything for it.