Some so-called "super-apps" are designed around payment system and create their own app ecosystem inside the single app. That is primarily use case for Asian tech - WeChat, Alipay, Go-Pay, PayTM, PayPay Rappi and etc.
How they manage to compile Apple's rules?
Short answer: They don't<p>Longer answer: They don't but they are so important to users in those markets that they would not purchase iphones if they could not use those applications there