I'm not entirely sure (well, about 95% sure), but it seems like the Personal Earrings obtained from the Character Quests no longer count as Earrings.
I.E.: using earring materials to upgrade them does NOT seem to give the same-type material bonus. Using 10 earring materials or 10 bracelet materials of the same grade yields the same amount of experience.
Maybe someone can doublecheck, but seriously, do double check, don't go by what you'd expect or what you "heard"!

Also note that when you use the filter, and set it to "Earrings", that the personal earrings no longer show up! (this is actually what made me suspicious, and caused me to investigate)