Complete and utter crap, they will work fine.
(AS LONG AS you have the appropriate charger for your country, which you say that you do.)
Batteries are DC devices, they get charged with DC power. Very simply the charger converts your local AC to DC for the battery to be charged with. (the charger does much more, but beyond the scope here). Keeping it simple, DC doesn't have frequency (hz) like mains AC.
Be careful with ebay batteries, can be just as easy to get fakes as "real" batteries.
amazon.com should ship most items to australia, they may be worth a look.