The gameplay mechanics answer seems good enough, but I think we can still come up with a normal in-universe explanation. How do we know that tabs were invented in Zeal? Because the Zealians say so. However, Azala has tabs, so it means that Reptites or at least Azala did know how to make a few tabs. Is it contradictory? No, because the only persons who said Zealians invented the tabs are the Zealians, and they obviously knew nothing about Reptites, they couldn't know that Azala had actually created a few tabs millions of years before them.