I didn't look that close to see what it was holding, just figured it was part of the fairing / headlight mount (I had a bolt in that same spot come loose on my C10, and that's what it was for).
It makes sense that it was partially responsible for supporting the windshield now that I think about it. When I was riding last week, I noticed the windshield was moving around more than I thought it used to, and was wondering why. Today, I didn't notice it moving (wasn't looking though), but I'll watch for it tomorrow.