The problem is testing resource and behavior issue. The behavior makes this necessary; The resources currently make this difficult to execute without harm to the airlines bottom lines. As more people start travelling, planes will be full, as flight availability is limited, which puts passengers and personnel at greater risk for now. Testing results would prove who is right in this case. Go back to problem 1 - testing resource issue.
I'm sure there were many factors affecting the 757. For me, as configured by or acquired by Aer Lingus - Very tight seating (I'm 5-8, 165 lbs); Flight attendants seemed to struggle a bit with aisle space. So challenging to exit window seat and transit aisle for a trip to the loo, seemed more sensible to hold it than go. Not easy on long flight. So glad Aer Lingus stopped using on my itinerary!
I feel sad for the pilots and their family, friends & associates. There is no reason this should happen. With hundreds of billions of dollars going ANNUALLY to the DoD for aircraft, warships, submarines, rail guns, missiles, radar, sonar, lidar, navigation, targeting systems - money is available. This relatively small and old fleet should be equipped with obstacle avoidance, tracking, air traffic control personnel and equipment. What if this happened over a populated area, such as fires have approached and destroyed in recent years?