And in what context would this yo-yo be used, exactly?

Typical use would be to fill it with Influence slime, let it fly. Can be used to section off areas with such, spattering and drenching potential targets and corrupting them more directly, spreading control over an area rapidly and before anyone can figure out what's going on, and I even have tinkered with the idea of enhanced maneuverability along corruption trails.

Another alternative would be fill it with seeds, like a travelling sprinkler of seed dispersal.

Neat!