I still don't get how and in whose favor this plays.

Management can't be in the union. So cripple the union by promoting the most effective members into management?

Alternatively, if you want to fire someone and the union blocks it, promote them instead, then fire them later.

> Management can't be in the union.

That's a weird rule. I've never encountered that in European unions.

There's a different gradient of workers union influence for employees at different levels. Traditionally, workers at the bottom of the pyramid have the highest union influence and it decreases as it goes further up.