As was explained years ago (it may not be in the current tutorial):

The spring and 'wedge' form a redundant lock, as '180 said, someone over engineered the mechanism.

The two parts serve to keep the locking cam from being pushed in, allowing the wheel to turn. But this is silly, the cam cannot be "pushed in" because there is no way to get in there and push it in, so, eventually, they stopped putting those two parts in.

And I shot some light machine oil in there before I put mine back together. I also wrapped tape around the mechanism, over the trap door, to prevent dust from getting in there. Over 65,000 miles without an issue.