After a purchase the app developer is the one providing content, customer service, app updates and bug fixes, etc. It stands to reason that a customer is doing business with the App developer not Apple. In all of your examples, they are products where the company setting the rules of the transaction is the same one that is standing by the product itself.
It seems completely reasonable to me that the provider of a good or service should be able to communicate freely and directly with their customer about something as core to the transaction as their options for paying for the service.
It seems completely reasonable to me that the provider of a good or service should be able to communicate freely and directly with their customer about something as core to the transaction as their options for paying for the service.