I don’t know why they said this — they really aren’t a viable alternative for weight-sensitive contexts at all. Their density is only abut 60% that of Li-ion batteries, and that isn’t even getting into solid-state Li batteries which are even more dense. If weight isn’t an issue, like for home or grid backup storage, they’re fine. For cars or bikes, not so much.

Your explanation is valid for vehicles that have 100% of their battery be something other than Sodium based, and also have a use case that requires long or intermediate range. That isn't all use cases. Vehicles that drive a lot, but never cover much distance would still be valid use cases for 100% sodium. 100% Sodium Ion powered EVs started rolling off assembly lines in Dec of 2023. Alternatively 100% Sodium Ion could also be for things like fork lifts or Semi trucks that move storage containers from a cargo ship to a storage location within a mile and repeat this trip dozens of times a day.

Other use cases would be where a car has some sodium batteries and some lithium based ones. The sodium batteries could serve most of the "wear and tear" of short trips, with a second smaller lithium back available to augment overall range which is not used as often.