I've been on the Hill quite a number of years, and every private member's bill that I've ever participated in did not regard the person who was moving the motion as a witness to the bill. The committee then would hear from them, often for two hours, including officials from the department. Each committee may do it a little differently. Then, after that, they would begin to hear the witnesses. But the committee is master of itself. That's just the usual practice that I have observed here on the Hill, and I know of no exception to that.
Evidence of meeting #13 for Public Safety and National Security in the 40th Parliament, 3rd Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was witnesses.
A recording is available from Parliament.