To be honest I am surprised WeChat is even allowed in the iOS app store with its all-in-one multi app experience, since app experiences of that type are explicitly called out as disallowed in the app store guidelines section 2.5.8 - https://developer.apple.com/app-store/review/guidelines/

(Actually, I'm not that surprised, they're probably too big to fail and Apple really wants to sell iOS devices in China)