Well with the oocca theory is that, the god's created oocca and oocca created Hylians or something like that. But what if the oocca are the descendants of the people from Skyloft and the oocca have merely evolved ,since it has been thousands of years. So if the oocca theory is still correct but, by replacing the oocca with Skyloftians then the Skyloftians created the Hylians therefore they have the same crest as the Hylians,or similar. Another reason is that because, like the Hylians, the Skyloftians believe in the triforce and the Goddesses it is just mere coincidence that the shield looks exactly the same, or Nintendo are just lazy for this trailer and hopefully they will create an entirely new shield design for the new game.
Either way I'm satisfied.