People do not learn at a constant speed throughout their education. Almost everyone has at least a few runs of "giftedness", at least in some subjects, where they could benefit from acceleration; and conversely, even gifted students might need some "remedial" effort from time to time.
A person with an IQ of 140 will learn pretty much every academic subject faster than someone with an IQ of 100. It’s kind of baked into the metric. Now, of course this doesn’t mean that they will have any advantage in learning, say, how to ride a bike or dribble a basketball, but the discussion here is clearly directed at “book learning” which comprises the majority of school curriculum.
