Weird that the manual actually shows the cupholder at the front of a
fold-down armrest for the "5-door"

.... Were they available in the 2003
GTs (and they missed editing this info out for the 2004)?
Actually Beth is my wife, I'm using her computer...

No, they were in the GLS from 2000 on, I'm guessing that this "item" on the
owners manual was just cut out of the GLS manual and pasted onto the GT
manual in advance of the GT sedan.
If you have the hatchback, look in front of and under the the rear seats,
you should find a "pull strap", pull up sharply. the seat bottom will hinge
up and allow you to "tumble" it forward (depending on the position of the
front seats). you will then see that there is no provision for the rear seat
cupholder. Sad I know, but if that's the only trade-off, I'll live.
Steven