Apple has changed that support page more than once. It was originally created in 2000 when the iMac was the only Mac Apple shipped with a slot-loading optical drive. From memory it warned not to use non-round CDs, but stated that the smaller 80 mm CDs were supported. As new slot-loading Macs came out (white iBook, PowerBook G4) the page was updated. Unfortunately some of the later drives didn't work with small discs. Even worse, some Macs have shipped with drives from more than one supplier, so there is no guarantee that any specific model will have a drive that works.

Eventually Apple changed the page so that it now says 'Some slot-loading drives may be able to accomodate 80 mm round discs, but their use is not supported and any damage caused will not be covered under your Apple warranty or applicable extended service contract.'