Ok, so I'm not crazy.
I contacted Thor and asked if they had diagrams of the ceiling construction. After a little explaining, I got a PDF (see pic). As expected, the styrofoam vent channel "ducting" is straight-through. In the diagram, the A/C baffle should connect to the duct with a shaped piece to direct the flow. This was not the case in mine. IT WAS NOT FREAKING CONNECTED!!!
I cut a small test hole where it should connect and found the duct channel (see photo from the forward vent rearward with my knife poking through).
I used a hacksaw blade to open up both sides and silver-taped it to prevent air loss.
Reinstalled baffle and a little adjusting - I now have what I expect for an AC system.
I really like my RV, but dang! Amazing the poor construction I've been discovering. *sigh*