When he says there's a physics problem with fuel cells he's not being flippant. They're less efficient than batteries, have lower volumetric power density, and cars using off-the-shelf batteries already match the range of gasoline cars (so there's no energy density problem to solve). The only problem with batteries currently is cost, and fuel cells are no help there.

Pretty much the only attractive thing about fuel cells is that they can run on energy-dense liquid fuels like methanol, which can do greater power fluxes than last-mile grid. But battery swaps are even better. Ultimately, lithium and gasoline have about the same energy density, methanol half as much, and compressed hydrogen about 1/10 as much. And there are good reasons why hydride storage is unlikely to become practical in cars any time soon.