Theres multiple angles on this and you might be the only one whos argued this. He was hacked by horford in this video and in you play it side by side...
He's clearly behind the line in that photo and if you look at the video you posted you can see that refs called it when Horfords hand was on Butlers...
I like the signing and I'm sure its a camp body but he can be an good back up to one of our tackles. He is a former first round pick that never lived...