I don't think they made the jump from the 13.4 to the 21.5 based solely on cell density improvements. 20Ah cells to 32Ah cells is a hell of a jump. Plus, if they had the same number of cells, there'd be no reason to dump the smaller internal-case design housed inside the split-channel air cooled shell. It seems much more likely that they went from 2p to 3p and got a slight Ah bump in the process.