I think the instructor is conflating two things here. If you are flying a standard 1500' circuit then I would do it exactly as you stated. However if you are above the max weight for circling in CONF3 with Gear Down there is no way I would conduct a Flap Full landing. There is always a risk that once Flap Full is selected you need to adjust profile which could include near to level flight. I would be conducting that circuit using only Flap 3 and as per the book 'DELAY GEAR EXTENSION TO MAINTAIN LEVEL FLIGHT'. So my plan would be to select Flap 2 with 10 seconds to run to the end of down wind and then once I have commenced the descent and are confident I am in the right spot then Gear Down and Flap 3.