First, cPython is 99% of Python deployments. So much that if a script works on it but not on another implementation, people often consider the later broken.

As this post proves that most people don't even know about this feature, you can be pretty sure the vast majority of people don't know about pypy, micropython, etc.

Secondly, even if you want to nit pick, Python 3.7 made it official more than one year ago. We are currently in the 3.9 alpha.

In fact, 3.7 didn't touch the implementation, just merely declared "yep, good idea, let's keep it that way".