You might be right about the main parachute. In WW 2, only US paratroopers had reserve chutes. This was likely a British paratrooper. So no reserve chute. And

You might be right about the main parachute. In WW 2, only US paratroopers had reserve chutes. This was likely a British paratrooper. So no reserve chute. And yes. Climbing out of a tree while shaking from adrenaline is scary dangerous. But it is the sort of risk that takes experience to appreciate. In WW 2, nobody had experience.