underdrive pulley install question

[Quadcammer]

Gang, quick question.

The pulley has a keyway that locks it to the crank. The crank is held to the transmission by the clutch which then goes to the wheels.

So, if one leaves the car on the ground for install, in gear with the parking brake engaged, the crank should not spin when loosening or tightening the crank bolt.

Can someone tell me if I'm missing something since all the install guides indicate that the crank must be held by external means when doing this job.

Thanks