I think the ability to manage either people or businesses varies all over the map, and between techies and MBA's, maybe it's like a pair of overlapping distributions. For managing people, I think that there are both positive and negative skills, and I'm not sure MBA's learn exclusively one kind in the absence of the other. Stack ranking and open plan offices had to have come from somewhere.

Negotiating contracts is win-lose, so it's at best a coin toss.

I could see certain tasks being performed by someone who has shown a motivation to learn how, such as making business plans, schedules, and contracts. The MBA's at my workplace are certainly busy. But it could be selection bias: People with MBA's are selected from among people who want to learn those skills.