It might seem I'm being a bit, or more than a bit pedantic, but the shaping of the apron doesn't actually shape the kilt by widening the hemline of the garment below the hips.
The construction of a kilt is a straight tube lower edge to hip which narrows into the waist.
The apron is shaped and wraps around the body so as to look right, but it doesn't make the garment flare out in the way that the panels of an A line skirt behave.

Anne the Pleater