Why rotate crank 45 degrees separate from cam when replacing timing belt?

2001(or something like that) Volkwagen Jetta 2.0. I read on all data after you lock cam at TDC turn crank 45 degrees? How are they lined up at all after that and what's the reason, I understand turning cam 1/2 notch when its a dual cam to release tension of the belt, but this makes no sense to me. The belts already off and then u have to turn the crank 45 degrees? Someone please clarify this for me and thank you.