>>6158085They made them longer so they are more screen accurate in dino mode. Them showing in robot mode as sides of the torso don't retract from the looks in any way in my opinion, the waist would look too thin without them.
In fact, they were painted in the actual suit waist. They based this on the toy mostly, but the T-Rex arms being longer and showing in robot mode seem to be a nod to the show props.
