How much flaps?
If it's FULL flaps, I agree with the instructor. Bad form with the gear not down & locked. Plus I'd like to preserve what's left of my hearing!
The sim profiles are a useful template for speeds and configurations to achieve during each the various segments of an approach. Most jets have one or more increments of flaps deployed before gear extension. Gear extension is often delayed until just outside the FAF or GS intercept. Now, with the gear down and green, landing flaps can be selected for the final approach without all that noise!
Of course each type has it's own manufacturer recommended profile and operators differ as to some of the specific SOPs and techniques, but the idea is to be on profile and in a good position to maintain a stabilized approach. In practice, the timing of flap and gear extension can be adjusted in concert with the noise levers to account for variables such as visuals, slam dunks, short intercept vectors or speed assignments! But keeping those profiles in mind as a template for where "normal" should be gives you something to compare against your actual progress.
If you know each of the sim profiles cold, sim training goes allot more smoothly. When you get on the line, that's when it all comes together and pays dividends. Enjoy.