1.1gb RAM in an iBook G4 - don't believe the tech specs

The Apple technical sheet for the G4 933mhz 14" iBook states that the maximum amount of RAM for the system is 640mb (12bmb built-in and one slot for additional).   Popped the RAM into the iBook, and sure enough both Mac OS X.4 and Fedora 8 recognized that now there was not just 128mb RAM, not just 640mb RAM, but a full 1.1gb RAM.   Has it made much of a difference? It's made a world of difference!  At least in Fedora 8, whereas I could not turn on desktop effects like having my workspaces on a 3d cube and the infamous "wobbly windows" effect, now I can not only have them turned on but I can use them without any sacrifice in performance. I can have as many apps open as I want, I don't have to wait for windows to re-draw themselves when switching workspaces...and so on. Huge difference. On my Slackintosh partition of the iBook, KDE actually has been running faster than Gnome <= Compiz, but I still appreciate the extra RAM once I start opening up apps or downlaoding one of the webs from the internets.  I am curious as to why Apple would say the limit is 640mb. Was it to discourage people from purchasing an iBook G4 if they were "power users"?  Perhaps; a similar technique has in fact recently been used when salespeople have been instructed to tell people that Final Cut Pro will not run on a MacBook — when in fact it absolutely does run on a MacBook without any hack or workarounds involved.  Or was it just that a 1gb chip of that kind of RAM didn't exist back when the tech sheets were written up?  I'm not sure...but the point is, I guess, not to necessarily believe all that the tech sheets say....!?