I am confused about the procedure for using the QR to remove my rear wheel.

When I bought my bike, they demonstrated front & rear QR in the store. But now I can't reproduce the rear wheel procedure. I can't figure out how exactly you are supposed to "rotate the rear derailleur back" in order to pull the wheel out.

For example, in this video, he does it at about 1:30:


The only thing that seems to pivot easily is that cage holding the jockey wheel, but the whole derailleur seems quite fixed in position.

Or does the derailleur only rotate after you have loosened the QR?
I know the thing is fragile - maybe I am just not twisting it hard enough? I'm afraid to break it!

What is the trick here?

Thanks for any responses.