Agar may also have ridden his luck, or just been more positive. For example there was some debate as to whether or not the third umpire was correct to give Agar not out on a stumping decision when he was at 6. After that there was a change of bowling from Anderson to Finn, and Finn maybe is a less consistent bowler and offered less threatening stuff. Or perhaps even the pitch was far easier to bat on than others made out.
Or, of course, Agar is far better than coming out last suggests.