As the history section of that PEP notes, it was actually written in part as a response to distributions like Arch changing the default Python to Python3. Although it's true that the PEP originally said that python should point to Python2 (it doesn't any more), it also said that code requiring a specific version of Python shouldn't assume anything about the system default Python, instead using either python2 or python3 - and requests that distributors of Python provide these commands.

This suggestion was adopted by nearly everyone, including Arch Linux. If you're writing a script that calls Python, you probably still want python3 as your command for compatibility across all current distributions.

In other words, the intention of the PEP was not to ingrain Python 2 as the "default" Python, it was to get people to stop making assumptions about what Python version they would get and use the python2 and python3 commands instead. I do agree that it has had that effect.