The earliest drawing of Beastling was basically a puppy with dragon wings.

Several of the ones that followed that had him walking around on his hind legs, and the influence of those drawings is that Beowolves can actually stand on their hind legs.

Part of it is that they needed to be able to use their hands as hands, so the ability to supports themselves without them was important.

But yeah, they're really built to move around on all fours.