The minimum OS target (which looks like 10.13) should ideally be well defined and tested using the latest SDK, rather than there being "no promises". Or at least it should be documented that this isn't currently supported, or how to disable specific features and which ones to disable. I downloaded the source tarball from https://www.python.org/downloads/release/python-370/

Python then isn't viable currently for embedding inside applications (https://docs.python.org/3/extending/embedding.html). 3rd party app developers on macOS typically have a policy at least supporting back to N-1 or N-2'th OS, and in many cases it shouldn't be their dependencies that drive this. 

The other two functions require 10.13:
futimens
utimensat

Fortunately the -Wunguarded-availability warning is enabled which spits out warnings on which functions aren't available when targeting a min OS (MACOSX_DEPLOYMENT_TARGET)

Can't say I can contribute anything here unfortunately :(. I had to do something though, so I hacked the configure scripts and pyconfig.h to make sure the clock_* and the above functions I mentioned above weren't being used. getentropy was easy to fix more properly because it already has a fallback at runtime in case it's not working, so it was just an additional NULL check. Looks like the functions are weakly referenced when building to an older OS target.

A bad step in future direction would be to continue making "no promises" and start using functionality only available on 10.14, 10.15, etc without fallback.