[samus]

The Win32 ABI is also just a wrapper on the native API, which is only stable in practice, but not officially according to any Microsoft documentation.

Glibc is userspace seen from the perspective of the Linux kernel.

[delta_p_delta_x]

It doesn't really matter if it's 'just a wrapper', because said wrapper provides an ABI. Even if the underlying Native API changes, the interface the wrapper presents to other compiled binaries won't. The latter will contain caller/callee register setup, type layouts, function arguments and more for that wrapper.

Cygwin is also 'just a wrapper' for the Native API and Win32, and look how drastically it changes the ABI of applications.