having heard that about 'lighter cores' i am still not sure it's true.
most of the interior and cabinet fronts and doors and table are 1x4s? solid stock hickory.
either glued together, or routed down.
some of the ply as a balsa wood core (the sliding doors) with very thin hickory veneers.
some of the ply looks like basic furniture grade (not chip board) ply with a hickory veneers.
the dining table is relatively heavy but the other things are light.
drawer boxes aren't hickory and the cabinet framing isn't either, but quarter round trim and edging is.
i think the main reason to buy from the source is matching FINISH, even on the ply, and board layout.
look at jerry's pics in the first link, those cabinets match perfectly for color and cut and so on...
the satin or gloss and clear color and thickness of the finish is pretty specific.
in fact there is a noticeable difference in thickness and gloss comparing PRE and POST 05 units,
with the later years being MUCH nicer.
even the factory service center doesn't have matching finish for repairs...
they sell cans of EXTERIOR acrylic panel spray (clearcoat) for wood finish repairs...
i got a pretty good match using some minwax wood finish for the thin or wearing areas.
almost 2 late to edit here's a link to an old pic of some of the thin veneer hickory used...