This control arm is also referred to as a transverse link, it is the one that goes straight across left right, with one end attached to the steering knuckle through a ball joint and the other end has a rubber bushing (203-333-09-14) attaching this arm to the subframe. The photo is of the inner aluminium sleeve of this bushing assembly, the sleeve has been separated from the rest of the bushing assembly.

This sleeve has an elongated hole, with four ridges inside, as you can see in the photo.. The bolt which anchors the bushing only fits in the middle of this sleeve, located by the four ridges. Apparently the ridges are used for camber adjustment. How does that work? Do you grind off two ridges so that the bolt can move sideways in the elongated hole?

There is a replacement bolt with grooves to hold those ridges on the inside of the bushing. As you found, the round bolt fits only in the center. The bolt with a groove can hold either the outer or inner pair of ridges. If you need that adjustment, install the bolt straight and be careful to hold it with a wrench and tighten the nut only. Otherwise, the bolt can be turned enough to wipe out those adjustment ridges.