If that were true, wouldn't you expect 50 year olds (who have mostly learned how to navigate life) to need little or no sleep? Seniors sleep only a little less than young adults, still 6-8 hours a night.

There are other known mechanisms in sleep, for example copying/condensing short-term to long-term memory by replaying it. Translating increased compression into better fundamental performance seems like a steep task and 50 year olds have already reproduced or not, so shrug