It is true that the U.S. over the last ~150 years has outperformed a lot of the world, but it maintained 7% real over that period of time. Ritholtz was all over the damn place in his article, and attacks the strawman of 12% growth. In comparison 7% has some backing.

Due to volatility, it is unsafe to retire on a planned drawdown rate of 7% (4% is a good rule), but it isn't unrealistic to expect 7% growth.