That doesn't say that the realm of darkness shouldn't have worlds. It only said the children built many other worlds, that's all.
It doesn't say it can't, but it does say this:
1. In it's natural normal state, a 'realm' is one giant world
2. To have many separate worlds, it involves that one world shattering
This implies that if nothing has happened to it, it is perfectly natural for the RoD to be one giant world. The many worlds in the RoL is an anomaly caused by having being destroyed long ago.
Didn't say there was a specific location.
No, but Nomura has said there is. Nomura said that the two realms lie on top of each other like disks, with the in-between realms like CO and Yen Sid's tower like stairs between them. This means that the worlds in the RoL are simply that; pieces of the old world floating inside the RoL, with big gaps between them, which is where you fly your gummy ship.
Plus the tale doesn't even seem like something that should be taken literally like many of you are, it's more of a story filled with symbolism. I mean, do you really believe little children got a hammer and started literally building worlds? No. And in all honesty, the whole thing looks like smybolism and imagery, which is why I can't take the tale seriously.
Can you really believe a little child got a giant magical key that shoots beams of light and went flying around the universe in a ship made of candy?
Think about when the worlds got destroyed during KH1. Did Simba have to go around with a hammer to fix his world? What about Beast and Belle, did they fix their broken worlds with hammers...? No, light just magically fixed them. I don't see why it's so hard to believe that the power of light in children's hearts could fix a world. This is friggen Kingdom Hearts, metaphors and imagery are often actually real. Shadows, keys, heartless...
I'm certain the story has a point, I never said it was pointless, but I'm saying that it shouldn't be taken literally or taken as complete truth.
Well, it's the only information we've been given at this point, and it's been repeated twice. The second time they repeated it had extra more detailed information and was in the very latest game to have been released, so I think there's more to it than you assume.
Nomura might have said long ago that it wasn't to be taken literally, but this is the man who retconned Xion that went against a lot of his KH2-era quotes.