While I agree that it's generally not helpful to rely on implicit atomicity in any Python, the reality is that all the other Pythons have followed CPython's lea

While I agree that it's generally not helpful to rely on implicit atomicity in any Python, the reality is that all the other Pythons have followed CPython's lead and implemented the same memory model for compatibility. PyPy, Jython, and IronPython all have atomic bytecodes. So, for better or for worse, this bytecode atomicity is a de facto part of the language.