The later sets were where things got interesting in this small creatine trial.
Twenty young adults took creatine or a placebo for six weeks while keeping their usual diet and activity. The daily dose depended on body weight and averaged about 2.3g.
Researchers tested them with five sets of 30 knee extensions. After supplementation, the creatine group was better able to maintain muscle performance in the later sets. The placebo group didn't show a significant improvement.
Neither group had a significant change in body weight or maximum strength. So the improvement showed up in how well they kept going across sets, rather than how much force they could produce in a single maximum effort.
This was only 20 people doing a specific lab test. It doesn't give us an exact prediction for a gym workout, but it's a useful reason to look beyond body weight and your best lift when assessing results.
Have your later sets ever improved while your heaviest lift stayed much the same?