If I had to guess I'd say it's that Google's rules aren't nearly as ridiculous as Apple's. For example Apple forbids you from even mentioning that you can sign

If I had to guess I'd say it's that Google's rules aren't nearly as ridiculous as Apple's. For example Apple forbids you from even mentioning that you can sign up to a service externally, let alone linking out to an external payment page. I completely agree with you though, there should always be an escape hatch.