Are we forgetting Cooper was told how to operate the stairs, had trouble with the stairs, and documents show the possibility of directions given to him about the stairs?
When did Cooper become a Boeing engineer?
I was once an airbag mechanical engineer for Allied Signal....on the team that pioneered them in the Italian market...yet I still have trouble opening the damn trunk of my wife's Jaguar, not knowing where the release or button was...
An engineer cannot be expected to know offhand all operability of every working part of the machine at first glance, though it can be assumed one fundamentally knows the all functionality of every working part....
This would be no different to a Boeing engineer with his career in the braking or flap system. He will likely fundamentally know the working of the aft stairs if told it's power source, but first time seeing might not know how to operate it..
I know exactly what you're talking about, see it every day. And the reverse is also true. I saw the whole work force change in the 60s from military trained people to 'credentialed' people who couldnt figure out what switch to throw! I saw it impact every walk of life. Finding credentialed people with actual work experience became a huge problem into the 70s. It actually shut down programs at places like NASA, Bendix, and JPL... so the disconnect is real. Was Cooper one of those? He lived right through the transition period.
Maybe Cooper's grudge was against 'managers' ?
Quite possibly, sure... the old school guys dont want to be marginalized, heck, especially those who took it on the chin in world war 2 with real risk and combat..these were real men.... And if Cooper was say, rendered obsolete by what he probably viewed as girly men who stayed behind and not sent to Nam...well, imagine the emotion there..... that'd be enough for me..... Tie that in with a midlife crisis and look out...😊
And I hope I'm not coming across like a moron here...for I'm used to a simple electronic switch release of the tailgate, with gravity pressurized pistons (that leak over time then slam my forhead on them) raising the gate... my mind is on something else, and Am not thinking of an electronic servo motor slowly opening it on command...nor where the illogical place in the cabin the Indian designer at Tata Motors (who now own Jaguar) decided to put the release button.
Relax! You have plenty of company. There is a car setting in my garage at this very moment with 15 miles showing on the odometer. It has a button on the "entertainment display" that says "clock" and I can push that and see how to set the clock and have done so.
The question is how do you set the "date", and it has to be associated with the "clock" display in some respect. But there is nothing on the dash, on the clock screen, or even in the handbook (!), about setting the date. I'll probably have to stop by the dealer and hope that they can show me how to plug in the correct date. 
If it is a digital clock, and only one button then it may be holding it down. I recall I think my mustang having to hold down a clock button then using the radio memory buttons in unison.
I do think Cooper might deserve a pass with not knowing safety release, and at same time be given far more credit for pulling it off in it's entirety.... I think he planned it and used deception, much more than given credit. For instance... Since he pulled off what I consider the greatest heist ever, having said that I think he use more wits... that he had a driver follow a pre planned route... He told them to fly south to mecx city but I'd bet he knew he was departing early, and knew the corridor would be the Reno one and/or planned to divert after takeoff... this would delay those waiting for him on ground... And having planned it all he'd have known the topography toward Reno and know to wait until the trees clear and a safe spot...He'd know they'd radio ahead after he jumped so to throw them off he could have bounced on the stairs to simulate a jump...and maybe the real jump later, timing the oscillation and diving out, sending everyone looking in wrong place..he had to know they'd be waiting for him so this deception was critical, maybe even THE most important part of the caper, was the getaway. Maybe even that squidding maneuver. But to do all this only to be waiting on way down....he got away with it so I'd lean toward a driver and deception in the jump.
