Bookstore / Market with In App Purchases

I am developing an application using ionic3 and the app is about selling digital books.

I created a web application so they can add books and their files to the platform. Once the books are purchased, they are downloaded to local storage and readable through the app itself.

Now I am considering In App Purchase as a means of payment on the mobile app but all the tutorials I have seen requires that I add the products to Google developer console and iTunes.

Do I really need to add products to Google Play Developer Console for Ionic In App Purchase? Myy idea is just to request for the products available in the database via custom API and use inApp Purchase basically as a payment gateway.

Possible? Crazy? Misinformed?