How is it not?

It's taking a side and saying that if you don't like the side they take then you can leave. The side they're taking is "we're above politics."

And "above politics" is the same as "not involved in politics". Call it a side/position/stance/perspective/angle or whatever else. It's still means they're not involved.

> "means they’re involved in preserving the present state of affairs"

No it doesn't. Perhaps constantly forcing your subjective interpreted and implied meaning on everyone else is the root of the problem.

> "call this being apolitical"

Sure, call it that. It literally means not involved.

https://www.merriam-webster.com/dictionary/apolitical

I still feel that you're missing my point but I am clearly not skilled enough to make it more obvious.

Your point is exceedingly obvious. It's being refuted by both literal definition and reasonable interpretation of the vast majority.

As I understood the "we're above politics", it was "you don't do politics at work". How is that taking a side? And if it is taking a side, which side?

Well, this particular policy change appears to have been at least partially in response to labor action that the company didn’t like, and if that’s not political than nothing is.