At the risk of being called out as the Internet Retirement Police, at no time did the MM family depend on the portfolio for their living expenses. In addition to the rental, Mr. MM did carpentry and other remodeling work for pay, and Mrs. MM earned the occasional real estate commission. Their assets grew substantially even disregarding the blog.
It's one thing to look back over a period of time, knowing the outcome, and say, see, the numbers show it can be done. It's quite another to sell your funds and ETF's every month to pay the rent and buy food, knowing that if things go bad, you have fewer options to recover as time goes on.
I think the folks over at early-retirement.org generally take a more conservative approach, with a keener eye on the risks. Yes, it's an older, wealthier crowd. You would think with more money available and fewer years of retirement to fund, they would be less conservative. But they are more conservative, and in my opinion, more realistic about the future.