As others have said the first order aspect of the crossovers has nothing intrinsically to do with the narrow range of the one driver, except that the designer evidently like first order crossovers and thought this implementation worked best with his drivers.
It would be just as unusual an implementation for Joseph Audio, with their steep slopes, to have a single driver with crossovers at 1k and 2k.
It would be just as unusual an implementation for Joseph Audio, with their steep slopes, to have a single driver with crossovers at 1k and 2k.