yes. i am sure the figure for limiting wear and tear was carefully calculated. they probably put some planes through tests to see how much wear and tear occurred after such and such miles.
break up speeds are more likely calculations as the test would kill the pilot.
common sense doesn't work well for you. last time it told you to ignore temperature when thinking about stress on an aircraft operating at altitude. now it causes obvious fatalities.
but unfortunately the wear and tear figures are no use for your conspiracy theory.
and your conspiracy theory also requires that the thousands of people who saw the commercial jetliners didn't see them. observation is science.
and the air speed of the united airlines flight at "sea level" was about 100 knots less than you are using.
awkward problem.