The article notes they'll be offering versions from 40-100kWh, the last being the 1,000 mile range one. As for why 1,000 miles, Toyota is running TV ads promoting 500-800 mile ranges of their hybrids. While no one needs that much for a road trip, it does eliminate any need to pay rural monopoly prices during one, and cuts down the frequency of trips to the gas station in local use; the weight/cost addition's minimal for a bigger tank (not true for a BEV).
With charging infrastructure still so sparse outside of metro areas, that kind of range (before you subtract for degradation, reserve, HVAC, winds, elevation etc.) would provide much the same worry-free convenience and flexibility that long range and the gasoline infrastructure does for ICEs. For a BEV to provide the same 300-400 mile + reserve real-world range as a typical non-hybrid ICE, it needs 500 - 600 miles of EPA range. This assumes that anyone would use such a car for such a trip, but there's little reason to so heavily emphasize efficiency for a city car, as it will be essentially invisible from an SUV in city traffic.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].
The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.