“Does this really differ significantly from a potato battery which is grown from soil organisms?”

Yes, massively!! The fact that potato can be used to create a battery is a consequence of the phosphoric acid (H3PO4) in the potato reacting with the electrodes. The soil organisms play no part whatsoever.

This virus battery uses genetically engineered viruses and carbon nanotubes, the fact is here is that the viruses themselves form a vital part of the conduction process. Reading the MIT article might give you more insight.