1964 Dart Wagon frame rails

'63-'66 Dart wagons are Valiants underneath (106" wheelbase).

Which makes them shorter than a sedan, right? Doesn't that seem backwards? Maybe it's fuzzy hindsight, but I think of wagons as larger, is there a reason why a Dart wagon would be shorter than a sedan or coupe? Was that the norm with American auto makers to make wagons shorter wheelbase?