All true, but I think he's talking about an arbitrary number of cells in parallel. If you made a 1s4p (one cell in series, 4 in parallel) pack with those same 18650 cells and had that magical 100% efficient voltage doubler, it would last just as long as the 2s2p pack and would be easier to charge (as you'd never have to worry about the cells becoming unbalanced.)

(Since the current would be doubled, the resistive losses in the wire would be quadrupled, but that's pretty small to begin with, and could be compensated for by making the wire thicker if you cared enough.)

The idea is sound, but I question the ability to make this voltage doubler quite so efficient (95%?) and have it work from 3v (a reasonable cutoff for 1s packs), and to do it cheaply enough to make this worthwhile. Really, I think the real answer is to include a balancer of some sort -- either include it in the pack, or have a separate charge plug with three contacts rather than just two and put it in the charger.