...but the pilot appears to have no backup plan in mind for an escape manoeuvre when the aircraft did not achieve the expected loop apex height and speed.
I'd be extremely surprised if a display pilot of AH's experience didn't have a backup plan. Specifically, the report details AH's own discussion of gates and what he would do if he failed to achieve them. The fact that there were gates in place means by implication that there was a plan should they not be achieved. Why have a gate at all if you're planning to blithely fly the manoeuvre regardless?
Therefore that indicates to me that he was either
unaware that he had missed his gate or
unable to react appropriately.