They use Python. They want to donate engineering time. They think this is a good idea. Why does there have to be a sinister motive?
I don't see any charity here, this is just a smart business move by them. When you run as many servers as Meta does being able to run 1/4 as many instances is huge RAM and therefore money saving. It won't take long to add up to 3 engineer/years.
They have the expertise to run a language fork and because of the scale they run at they would easily save more money doing so. Meta contributing to OSS is not an economic decision. It is about branding, trying to attract technically strong individuals (who tend to contribute to OSS or want to), and sticking to their open culture.
Actually, experience has shown the opposite to be true. Time and time again even large organisations find their fork falling behind the community version and the pain of merging new versions from upstream grows and grows
You could maybe make the argument that they're trying to swing priorities if this is considered valuable but less valuable than other things, but give the PSF doesn't actually employ anyone who it can direct to work on specific projects anyway, how is this any different from the already existing prioritisation process of "things that somebody is interested enough to go through the PEP process and then work on"
We all remember the anti-OSS 'Linux is only free if your time is free'.
The alternative is Meta puts in no money to salaries and benefits for up to three individual's time on this project, or Meta puts in no money at all.
Meta is paying, one way or another, for this project.
Did I deny this?
To put it in extreme clear example, just said time for someone to punch you != time for someone to work for you, while money is same all across. I hope you don't disagree with it.