I agree coming off the upper deck of a 747 is going to be about as bad, but there is no where near the amount of people on the upper deck of a 747 series aircraft.
If they are trying to move that many people off the upper deck there will be some anxiety involved, people just can't ho hum there way to the door and expect to make 90 seconds. Have a few of them fall and get landed on by somebody moving that fast will certainly get people hurt. Imagine the bad press if somebody happened to get killed during the test.
