People are just making assumptions on what the Dev head said. He never mentioned the size of D1 maps at all. All he said was that " the EDZ is the largest destination we have ever created, maybe by a factor of 2" (direct quote from their "Destiny 2 Gameplay Premier - The Worlds of Destiny 2" video, at about the 1:25 mark). This could be comparing it to D1, but it could be comparing it to other playspaces in D2, we just don't know. For all we know the smallest destination could be the size of Cosmodrome plus Plaguelands, which would make that "factor of 2" comment have some weight. But, again, we just don't know. For all we know he could be comparing it to playspaces from other games that Bungie has created, such as their Halo days. We will find out during the Beta just how big the playspaces can be, but until then it is all just word of mouth speculation.