Electric motors/generators are in the same range. Also I doubt they need to target the best possible chain bikes in order to be a viable solution.

Since it has a battery and the battery is (most likely) chargeable, a little loss of efficiency is inconsequential. On the other hand, having an actual physical chain on an electric bike seems indeed unnecessary - at least for less sporty applications, where things like "feel" or precise power delivery are not important. The end result will be a simpler, more reliable bike. Not to mention better looking.