Example: Let's take r=0.1, g=0.03. Consider a Rentier with a real investment income of $100,000/year (ie, off a $1M endowment), and a Worker with wages of $100,000/year. For simplification, let's assume both individuals spend their entire $100,000 income every year.
If you follow the r>>g hypothesis, you might assume that after a period of time, the Rentier will be far better off than the Worker. But that's not the case. After 20 years, the Rentier's real income will still be $100,000/year, off the same $1M endowment. Whereas the Worker's wages will now be $100,000 * 1.03^20 ~= $180,000
Clearly a higher r will be to the Rentier's advantage, especially if he supplements his investment income with wages as well, and keeps growing his endowment further. But this is going to be true even for r<g. There's nothing special that occurs when r overtakes g, since they are comparing totally different things.