That phenomenon probably has more to do with wealth being spread increasingly thin across ever-larger generations
Though your point is valid it's only part of the story.
I've seen many scions from China attending western universities in a state of decadence, barely focused on their course work, all too willing to live off their parents' past efforts, while driving expensive cars and walking around in clothes and accessories worth tens of thousands of dollars.
Even the "probably" is wrong. :)
Certainly more offspring was normal, the further back you go. So wealth division could more easily happen.
But most cultures had the idea of the "first born", the official heir... for this very reason! Most of the loot, holdings, tended to go the eldest.
Yet the proverb is historical, as all proverbs are, and my response was intended to refute the dissolution of wealth, historically, by spreading it too thin.
Our ancestors didn't do that.