Well it is obvious that the father does this when his son is a 20 yo. And it is obvious that this is a clever hint. My point is why not to do this when his son is 10 yo?
That said I feel I still have plenty to share with my children and now grand children - each day is a gift and each one will have mundane tasks, challenges and triumphs that all need to be dealt with accordingly.
Maybe at ten the child would be able to understand the words, but do you really learn the lesson when they have not yet spent a decade of being a teenager that is now over?
At age 10 you're still truly a child, you don't know shit about shit. Age 20, you still probably don't know shit about shit, but you might