Instead, Rob thought he had all the time in the world to make the central pawn break and played 12...Bb7?!, setting up extra protection for the d-pawn when it does go to d5. Play continued 13.Re1 Re8 (he can't now play ...d5 because the e-pawn would hang), reaching the position on the right here:
Indeed, this is a common theme in the opening black chose; in many lines of the Benoni, white snuffs out a potential black pawn roller with a timely a4-a5 advance to make ...b5 impossible without allowing an en passant capture. A common way for black to stop this is to play ...b6 before the pawn reaches a5, thus ensuring that the en passant capture never takes place. The same idea could have happened here as well, with ...d6 on move 12 or 13, which would alter the dynamics of a c5 advance from white.