Not sure there is an understanding of how qualifications work.

You got a bare CPL, so you are bottom of the rung of Commercial Pilots flying VFR single engine. Not many jobs, limited locations those jobs exist with word of mouth being the prime way to find them.

You added a G3 FIR to the base CPL, you are not anymore qualified as a CPL, still bottom of the rung VFR single engined pilot, however you expanded your possible work to Instructing. Like the bare CPL, there is still very limited work in specific locations for a new hire with no experience. Being overqualified is not a thing in aviation as you are paid for the job you do, nothing more. You get hired as a CPL charter pilot, your G3 FIR means nothing, unless they further employ you to instruct on the side. There is nothing in the Award or any EBA I know of that will pay you for qualifications you do not use as part of that employment.

Well, there "being overqualified" in the sense that the employer is suspicious that you are fully capable of another, higher paid, position with another company and suspects that you are in fact planning to move on as soon as possible, that this application is just to fill in a bit of time...

That doesn't apply here, though. :D