I saw this photo for the first time a few years ago. Sure, it could be Putin. Sure looks like him. But it also might just be a Russian tourist.
Let's break this down: Have all the other foreground people in the photo been identified? If all the main (foreground) people are identified except for Putin, that would be for me a very strong indication that it is actually Putin.
Remember that Reagan was nearly assassinated early in his first term. I find it extremely unlikely that anyone would be allowed that close to Reagan unless they were identified. Some random dude with a Camera is not going to be allowed to get that close to the US president by Soviet security, let alone US security.
So if "camera guy" is NOT identified officially, then who would an unidentified guy within Judo throwing distance of the US president be? A spy, of course.
If only "camera guy" was shirtless and riding a horse. Then we could more easily identify him...