> only requires agency from the party assuming control

It's a political concept. It requires agency from the actor recognising the threat. We're pretty close to being able to hurl a giant rock at Mars. That doesn't by a long shot mean we "control" it.

If there were a human settlement on it, on the other hand, being able to credibly threaten Armageddon does give the thrower control.

I see your point.

In the original context of Dune Paul controls the spice because he can destroy it and his will would survive but it would destroy the way of life of the other cultures. So saying "Paul controls spice" only makes sense because another entity needs it and what's really meant is "Paul controls society".