I don't see how it would kill web freedom. If anything the reduction of duplicate work means that the web can evolve faster to better compete against its competitors to stay relevant and attractive for developers to target and support.

>The Linux kernel is an implementation detail on Android

The kernel is such an important part of an operating system, you can't really ignore it as a developer even if technically it may be an implementation detail.

>Any use of Linuxisms on Android apps is done at user's own peril and possible kick out of PlayStore.

Sure, but Linux's ABI is stable and even in a world where things are moved to Zircom starnix was made to support that same ABI.