My best answer to this is the pilot recognised it was going wrong (engine power variation) and this was his best effort at an escape manoeuvre. Enough has been said about hours on type, currency, recency. A hunter flopping out of the vertical deserves respect and the escape manoeuve you described would be a hunter expert version, flying to vertical down, gaining speed and then pulling is the safer version if you have spare height.
Are you saying the Shoreham Hunter flopped out of the loop? I don't believe AH ever attempted an escape. Been mentioned before, but you'd never want to escape from a loop by putting the nose vertically down to gain speed, then pulling out. Speed may be very slow at the top, but you don't need to wait for another 90deg of the loop. Nose 10-40 deg below the horizon will suffice. Speed building rapidly - roll upright then ease out of the dive.