Do you have any firm links? because there was always a lot of unnecessary confusion on this one.
I thought Prog scan was done in the software, and as the Component cable is an official PAL product that uses the Digital port all those early rumours of it being disabled for PAL etc etc didnt have any grounds.
I have one of the first batch (I presume) of PAL UK cubes and Progressive scan works with all my US games(that have progressive scan option) via freeloader, although admittedly I struggle to see the difference on a projector.
Anyway what clouds the matter is that according to some of the posts on here it works for some and not others, I've noticed my projector automaticly detects the option and gives me the choice without holding the red button (is the signal sent back to the Gamecube? or maybe the selection text is always there but only readable on some devices or all whenl a red button is pressed), and yet on component TV I have to hold the red button.
Also the intro screen on Metroid Prime has screwed up colours on Prog scan mode but the rest is fine.