Unless you rake it at the perfect (direction of cut raking into the heads or the angle of the rake arms) it will either ball it up and plug up the throat or stand it straight up and form a ball that clogs under the arms or wrap a wheel. Don't even try it at 90* to direction of cut. If raking from the cut end it won't start moving it till about halfway up the stalk. Then it gets between fingers and will wrap or fall out behind.
Disclaimer.
It rakes fine grasses like orchard or fescue and clovers as pretty and even as any rake. Johnson grass under say under 3 feet it does fine with also. It also doesn't mind spotty Johnson grass. It's when you have large patches (we have some fields with over an acre of solid Johnson grass) 6-10 feet tall that it hates.