Again, no offense, but the set of people who understand child development and the set of people who would say what you said do not intersect. So I can infer that you do not know child development.
There are two questions here: (a) what's the actual value of this idea, and (b) what's the right thing to say to a child who has come up with an idea like this, in order to give them the correct amount of encouragement without over-praising them?
As the cold-hearted over-educated curmudgeons of the internet, we're allowed to answer part (s) without worrying about part (b). The kid's dad has to worry about part (b) for himself, but I hope the kid's dad has enough perspective to realize the correct answer to part (a) is that it's worthless.
I don't really think any reasonable reading suggests the kids dad was asking question a. Do you?
In the future I would strongly encourage you to leave out remarks such as, "You should understand more about child development." I don't mind if you state that I'm wrong, for clarity, but you don't know anything about how many years I've spent learning about child development, or how much I know about it, so it's not wise to comment on that.
PS I upmodded you back to 1. I don't think you intended to be hostile.