Except that he needs to pay to, y'know, eat and have a place to live and all that other life stuff. I'm assuming he doesn't want to live with his parents forever, even if they're cutting him a deal. 8% is likely an unrealistic growth rate anyway.
Here [1] is a calculator for investment fund returns. They're quite insane. Pick the absolute worst period for returns bust to bust 2000 to 2010 and you're still looking at a positive return. 1990 to present and you're looking at 10%. 2000 to present, going through both busts, is 6%. 2010 to present is 14%. 8% is not unreasonable - let's say it accounts for him possibly getting a raise sometime in the next 22 years.
I'm not even all that sympathetic to the worker in the article, but "just park all of your money in an index fund and you'll be a millionaire" is quite naive.
I think the thing many don't see is that in spite of people continuing to fail at life we live at a time when it's far easier than ever to succeed. But most people won't do the ideas espoused here since it requires discipline and planning. Instead they go drop their paycheck off at the pub, buy all the latest electronic toys with built in planned obsolescence, and so on. Or he finally hits $20k in the bank and then decides to go blow it on holiday to Asia.