In the final jump scene one of the paratroopers is smoking on the aircraft. Smoking has never been and is still not allowed on military aircraft or the flight line because of the danger of igniting fuel and munitions. This was especially enforced in the era of propeller aircraft because of high octane, very flammable aviation gasoline.
When the two parachutists land in the river their parachutes are not deployed but still packed. These are the jumpers main chutes, activated by the static line when jumping on command. These two jumpers, however were using their emergency chutes. The sergeant even tells Burke to remember to pull his ripcord. Therefore, the main chutes would normally remain packed.