No its not the true function lol. Your just saying that because a ifbb pro told you to lockout so you must assume its the "right way". No way you know the full function / range of motion of the quads, not taking a shot at ya, just making a statement.
Is not locking out the right way? You can fully shorten (contract) your quads without locking out your knees. Though its takes practice.
If you have any "lagging" muscles, im the guy to talk to for that. Remember that. Its almost a night and day results after working with me.
Merry X-mas!