Not ignoring you Paul, just haven't run across that myself.
I do know that up in the headliner there is a rear sunroof drain on either side that has a connection point back there towards the C-pillar to a rubber tube.That rubber tube that runs down the C-pillar can come loose and allow water from sunroof channel to run down the side back there.
I haven't ever explored the rear vent area although when spraying these off at the car wash I've often wondered what would happen if I sprayed right into those slits running down the C-pillar facing the outside.
Hopefully somebody else has seen this. Be patient and wait for the right person because, to be honest I can never remember this being discussed.....

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John