What logic? The Econoline doesn't have the variety of configurations, volumes and payloads of a Transit.
So far Roadtrek has been hesitant on its Transit plans and Hammill already publicly stated reservations because the cost differential is not that great with the Sprinter and he expressed the luxury brand reputation was a factor. Whether Hammill was blowing smoke to belay competition and anticipation, no one knows. The ace in the hole, though, is the Transit is American made and the dealership is widespread. Those two factors should resonate well with a large segment of people.
The Sprinter still holds an advantage of volume and payload capability over the Transit but the Transit I think has a wider advantage over the promaster in volume and load as well as practical design considerations especially for under floor.