Yeah, that's true. The fork cap pinches the top clamp. But its not that great of an attachment. It still has wobble because the top triple clamp can spin on the forks and get out of whack with the bottom clamp.
The fork cap just pulls it up, it doesnt do anything to keep the fork tube from spinning in the clamp. I use the term spinning loosely, its just a fraction of movement.
While riding forks are bending and flexing here and there. If you have ridden dirt bikes often, you'll find your front wheel and triples out of alignment every so often. Especially after a crash or bounce the front off a rock. Sometimes you fix it real quick by kicking the wheel back straight. If you have the time to fix it better you loosen everything up, straighten it all back then tighten it up. Similar the savage forks are moving around a bit too.
The triple just tightens it up a bit. A fork brace tightens it up just a bit more than that.