My main 'issue' with his numbers is the car purchase. Saying he only bought it because of the blog and thus not including it is disingenuous. If the purpose was just for the blog, why not keep the old car, and work out some longer-than-normal-term rental on the Leaf? That would be a business expense, generated solely for the blog. To me, it seems like he wanted the new car, and found a way to justify the spending (for the blog!) and to justify leaving it out of the spending numbers (business!).
I think MMM should count the new car as spending. It's a single year thing, so if he wants to spread it out over 5 or 10 years, sure, we would grouse about predicting the future or accounting tricks, but at least it would be accounted for as spending, and not tucked down out of the way as a footnote. He already takes the final number and subtracts out things to give a 'bare-bones' number, so why not add in the car purchase, then remove it too.
It's understandable that MMM wants to project spending as the ongoing routine categories and leave out the big isolated one-time expenses. It makes it easier to track year-to-year, and comparisons are clearer. However, so many expenses in life are large one-time expenses. A renovation, a new car, a new roof- all are expenses, and should be treated as such.
FWIW, I had to buy a 'new' car this year. (Yes, had to- the old one had an unfortunate incident involving a concrete highway barrier and a snowstorm.) I account for this in my yearly spending, since, you know, I paid money for it.