Linking with newer SDKs is needed to get access to some newer features and APIs. That's less relevant for Python itself, but can be relevant for the embedding application.  You can still compile Python itself on an older machine, then link it into an application build against a newer SDK. This does make the build process harder though.

However, there seem to be some issues when you mix code linked for different deployment targets, for example <https://bitbucket.org/ronaldoussoren/pyobjc/issues/174/crash-using-dictionaryservices-on-1012>.  This is issue contains a C extension that works correctly when CPython is build with a new SDK and crashed hard with the interpreters on Python.org.

This is one reason why I will at some time in the future look into this, but I cannot say when that will happen because I have limited time to work on this.