Apple appear to be using the same rules that they made up when "allowing" third party browser engines in the EU. It's worth pointing out that these restrictions are such, that to best of my knowledge, no one has shipped a browser with an alternate engine in the EU app stores yet despite being permitted to for over a year now.

The demand that the application with its alternate browser engine must be a completely new and separate binary from any app already using the built in browser makes it hard for existing big players like Chrome - they would have to manage two apps on the store during any transition to their own engine, which supposedly has been one of the biggest stumbling blocks for them already in the EU.