In addition to social security, of course!

"I suspect that most people, if they knew they were going to have a 12% rate at retirement"

Not at retirement. non-stop, 12 months a year, cradle to grave, for all people without non-primary home/non-student debt. If you owe money on a vacation home, couch, car, etc, you aren't allowed the 12% account-- any debts on anything but your primary residence will be automatically serviced by the account.

"Of course, none of these numbers assume any effect of inflation, which is the elephant in the room of financial planning."

An inflation target of 2% will be insignifcant in the face of the 12% interest rate. Current methods for inflation control can be employed, additionally, inflation shall be flattened by the reduced use of credit.

" And when it is all said and done, it is a little futile to have any discussion of this kind in terms of money rather than real assets. "

The real asset here is human labor, which is priced at a minimum $7.15 an hour in dollars. 100k is a nice round number equivalent to over 5 years of minimum waged labor, but less than 10.

"What if the oil runs out completely by your retirement?"

I think oil will cease to be the key transport fuel of the world by 2025. I'm not sure what will win yet as the new long-term champion, but, I'll probably be buying an electric car next time I am forced to purchase a vehicle.