Sometimes someone skilled at hitching can actually achieve a sort of 'knee kick' to get the bar up.
I believe the uneven lockout rule was put into effect when people started twisting back and forth so much to get the bar up the spotters, as well as the judges, were not sure if they were going to fall off the bench. Since it is impossible to say how much is acceptable, as that is far too open to interpetation, the uneven extension rule was imposed.
I believe that the hitching rule came into play more to differentiate the lift from the Olympic style pulls where a rebend is pretty much the rule.
As a point of curiosity, in PL competition, I have only received red lights for the obvious reason, was not strong enough and missed the lift. Never received a technical.
OL'ing, OTOH, I received quite a few for incedental contact in the bottom of the clean due to my short torso and long arms, until I learned to begin to whip my elbows around and up much earlier than most. Still picked one up for that every now and again though.
Dammit.