Sliding genioplasty & chin implant removal together or separate?

I was wondering if it is best to remove and replace a chin implant with a sliding genioplasty in the same procedure or remove the implant and wait 6 months to see how much the soft tissues shrink back down? A surgeon told me it’s best to remove & wait 6 months to see how the soft tissues go back down. His reason was that then he would know exactly how many mm to bring the chin forward, otherwise he said it could increase the changes of over/under projection if the tissues didn’t shrink back down.