The commonly cited number refers to when the brain structures stop/slow development, not the halting of skills or knowledge growth.
https://en.wikipedia.org/wiki/Human_brain_development_timeli...
https://en.wikipedia.org/wiki/Human_brain_development_timeli...
> There is no actual evidence suggesting that impulse control only finishes developing in humans in the twenties. It is a common misconception in popular psychology that the brain only fully develops by 25.[13] This may stem from a misinterpretation or oversimplification of studies which determined that development of the prefrontal cortex continues into the mid-twenties
>Human brain maturation continues to around 20[10] to 25[11] and even up to 30[12] years of age and beyond.