I think the big flaw is in the assumption that you can spend an entire month's earnings in a single month. If you ever find that happening, it's a huge red flag that you're doing things wrong.
A much better way of looking at finances is to adjust your lifestyle so that you require a tiny, insignificant fraction of your income to survive. As developers (and freelancers), especially as a young one, this is quite easy. Cheapest apartment available, same old car from college, roomates, no television or electronic anything, etc. Fit your life into $20k/year.
If you do that (and if you're fresh out of college you'll have just survived five years of doing exactly that), it's pretty hard to get yourself into a spot where money is an issue if you have any sort of professional job. Even if you have the roughest year imaginable and only book $40k worth of work, you'll still sock away $10k into savings.
The author touches on the concept of having a full year's worth of living expenses in the bank, but immediately dismisses it as if it were some impossible ideal that nobody could ever achieve. But he could, in a single year at the rate he seems to be billing, if he really wanted to.
And there's no way of explaining just how liberating it is to have that sort of personal runway. If you don't have it, you need to drop everything and make sure your only goal in life is to get that $10k-$50k pad into your bank account.