Re
"he reason for the odd layout is so you can get full defrost simply
by shoving everything to the right and setting the blower to speed
2.  Why VW thought that was important is not clear to me. "

The Reason for that is Safety ... as in getting the windshield clear
quickly.
I suspect that hardly anyone knows  that the little diagram there ..
showing all levers to the right and fan on # 2 is a Federal Requirement...
due to safety reasons.

short version is ....both bottom levers to the right and you won't' get
air to the knees..
IF all cables are working smoothly.
btw, for the original poster .........the heater valve cable ( Temp )
notoriously does not get lubed , like ever.
What happens is ...
increasing temp pulls out the cable, decreasing Temp pushes the inner
cable back into the outer cable..
it gets sticky and dry ...there is over an inch of unsupported inner
cable...finally one day that area just kinks,
then you don't have full control of the heater ( temp )  valve. It's
easily prevented too.

trimmed