Except that python says that python 3 should be an executable named `python3` and `python` should refer to `python2` [0]
"...however, end users should be aware that python refers to python3 on at least Arch Linux (that change is what prompted the creation of this PEP), so python should be used in the shebang line only for scripts that are source compatible with both Python 2 and 3..."
There was no guidance before the Arch devs made their choice. There's no reason to change back.
Especially since the goal is that python3 will be default eventually.
"...in preparation for an eventual change in the default version of Python, Python 2 only scripts should either be updated to be source compatible with Python 3 or else to use python2 in the shebang line."
Well, the answer is that this is a silly discussion. Arch is doing what Arch is doing because Arch is intentionally forward oriented, sometimes to the detriment of backwards compatibility with the old school (and yes, a distro not having a symlink for python2 is at this point nearly 5 years into being "old school").
Arch's change angered many in the Python community, and broke a lot of code. That Arch refuse to adopt the established convention, because it would involve admitting a mistake, shows a distinct lack of professionalism.
Well, until developers that do their work on other distributions start getting bug reports as a result of Arch's unexpected naming convention. Should someone outside of the distribution expect Arch to change so that their software works there? No. Should Arch expect outside developers to adapt their code to work on Arch? No. Honestly, I'd expect the kind of people that Arch attracts to be used to dealing with little snags in operation, and for them to just dive in and fix it on their own.
(Normally not a Windows user so I have no idea why this is the case or if by design.)
https://www.python.org/dev/peps/pep-0397/
As you say though, it doesn't rely on the names of the exes.