> I think we're waiting here for the release manager to decide, right?

As Petr mentions, the release manager doesn't have authority to decide if the backwards compatibility policy can be ignored, only the Steering Council.

> Should we roll back the change to PyCode_NewWithPosOnlyArgs() or keep it?

I don't think is possible: code objects must be constructed with the new argument, otherwise they are broken. There is not an easy way to have a default for PyCode_New and PyCode_NewWithPosOnlyArgs that somehow creates the field from nothing. 

I *personally* think that this case is one good example of an exception to the backwards compact rule, but I myself cannot grant that exception as a release manager. I also think these APIs should be removed from the public C-API ASAP because they literally conflict everytime we change the code object for optimizations.