> But, should I just continue standard practice (sys.platform), or would
> this be a moment to move towards platform.system() (i.e., set the
> example to be to use "run-time" rather than "build-time").

Oh, now I'm confused :-) I checked the Python test suite: some tests use sys.platform == "linux" or sys.platform in ("linux", ...), some tests uses sys.platform.startswith("linux").

In case of doubt, I suggest to do nothing :-) Leave the code unchanged :-)