It's not a travel. Allen caught the ball while taking his two steps backwards. Manu's done it before. Remember that game winner against the Bucks a couple of years ago.
Anyway the whole business of contesting 3's is ridiculous. It's like playing the lottery. I bet there's not that much of a difference between the percentages when you consider contested and non-contested 3's. The only way to guarantee a 3 doesn't go in is to run the shooter of the line. Especially when you're up 3. Force them to take a rushed 2 pointer but don't allow them to take a 3.