why aren't the frame rails of TT set evenly from the sides?

actually, re. the coupler...looked at that...at the very front of the trailer is a plate welded across the front of the frame rails...the rails themselves are not visible...the coupler is (as logic and physics dictate) mounted right in the middle, but it's mounting point is this plate in front of the frame rails...

no way to tell how the rails themselves are configured...they're blocked by the plate at the front and the plastic sheeting under the unit