I don't think he saw the photographer. Yes, he saw the proposal, but where he "crosses" only matters because of the photographer. I wonder if he got separated from his party (they went one way around the proposal, he went the other).
As far as "public proposals", I proposed to my now DW in front of the castle (really in front of the castle, not in the street). It's because she's a Disney nut and I wanted to make the proposal extra special to HER. We didn't have photographers or even any family members (we left them at DHS).