Some of the stones have a different pattern. Sometime if I'm in the mood, I'll compare the rubble stones with the ones on the right to see if they were pasted to fill in on the left. Or vice versa.
They would have had to have someone take the photo as people didn't have digital then. Even if they did, you'd have to set up a tripod or something further out to set the camera on for a full view. And then a way to trip the flash which most people don't carry around a remote for that.
The people who have worked on this are considered crazies, fully discredited. That Zullo seems pretty sharp to me.
I don't keep up with it any more.
Check this out. The wall:
Obama stand-in on bench at East 61st Street and 5th Avenue, April 3, ...
The dip is right. But the background in the photo at link (can't get to the "visit" page for more info). But it looks to me like except for the tree, the details of objects behind the wall are "busier" with people than the trees/shrubs only in the WP photo.
Somebody posted B4 on FR. The bench with nobody sitting on it. You can find it at the link along with some irrelevant images. You can pick out my search terms if you want to do it yourselves.
FR thread with lots more commentary except not the address in 2013 here: