That is exactly how the DD washers work. Normally, when there is nobody to open the lid and interrupt the cycle, as the dial turns to spin from drain, the motor is briefly shut off. When it is restarted, the tub spins. There is a slight click when the motor stops as the tub become engaged.
You will notice, if you open the lid during the drain, the motor shuts off, and you will hear a slight click noise. When you close the lid, the machine will drain and spin. By interrupting the drain, you caused the machine to spin prematurely.
Joe