He also gives 2 other options that would lend towards maxing it out fully... I just don't want people reading this to get the impression that MMM says "Don't max out your 401k."
Right, but there is more than 1 way to skin a cat.
For instance, if you only had enough to max your 401k (and no more), and have done so for many years, and decided that 2012 was the year to retire early (yay!)... you might end up having a bad time. The 120% rate for SEPP payments is
terrible right now because of the 30yr treasury rate.
If this hypothetical 401k-heavy person was 40 years old, and wanted to start SEPP's at today's rate (1.1% ?), they'd only get $28k/yr on a $1M 401k stash. Not the most stellar of options. Not to say that you wouldn't be able to swing it, but people have all sorts of different situations, and like to have options.
Edit: I just re-ran a scenario where this hypothetical person did the 401k -> Roth IRA conversion pipeline method with 340k and SEPP with 660k, and they would manage to get $36k/yr. So, I suppose you still have some "options" with a 100% tax-deferred portfolio. But, that Roth Pipeline takes 5 years to set up.