I've seen it first hand.
My dads cousin is an electrical engineer. The fucker figured out how to watch satillite TV wink wink, and a bunch of other shit. Totally into HAM radio building all sorts of other electronic gadgets and do dahs, but he had to have my dad help him change the spark plugs in his car once.
Once because my dad said he'd never help him again.
Started out with him taking EVERY spark plug wire off of the plugs, making no note as to where they went.
Then he took the hood off the car.
I have no idea why. I was 15.
Then he took all the wires off of the distributor.
Finally he gets to taking the plugs out 4 hours later and by this time he's dripping with sweat and covered in engine grime.
He eventually gets all the plugs back in, and asks the million dollar question to my dad who was busy working in the back yard machine shop, attempting to make a living.
"What order do the wires go in?"
It was a Ford, so my dad didn't know the firing order off the top of his head, and they spent the rest of the night trying to get it put back together correctly being that NO ONE knew the firing order on this car, or where the #1 cylinder plug went on the distributor cap etc.
My dad can still change a set of plugs and wires in about 15 minutes to this day, but his cousin still can't figure out the procedure and pays someone else do it for him.