I suspect that there are also a lot of EREV reservation holders that are not fully aware that they'll be getting a much smaller battery than the 350-mile BEV. This was not a well publicized fact in the first few days of reservations. I initially reacted with "how would you not want the EREV' until I discovered the difference in battery size, then changed my reservation to BEV.
There are several factors that determine the battery size in the EREV. The biggest is the cost, and nearly equally the packaging space. Reams of data show that, on average, people only drive 30-40 miles per day. 150 miles of pure battery-electric range covers the vast majority of daily commutes in the U.S.
By reducing the battery size, we also lower the vehicle's cost and weight. If we were able to package the full BEV battery, a fuel tank, and an engine in the Traveler, the vehicle's cost would be significant. Having a smaller battery reduces cost, moves the weight forward for better weight distribution and provides room for a fuel tank under the rear seat area of the Traveler.
Final battery size (and chemistry) and fuel tank size will be finalized very soon, and we will know more about the specs once all testing is completed.