There is no separation of immigration or customs. All CBSA are agent. They take care of both immigration and customs part.

Your reply to the questions and the code marker on your form by the agent or the kiosk sealed your fate. After your bags are picked up the agent collection the form will send you to secondary base on what is marked on your form. This last agent also have the right to send you to secondary if anything does not look right (you and your belongings).

These are facts given by a trusted CBSA agent during a social, speaking off duty.