My original interpretation was:

"The Dark World is non-existent unless Ganon is alive and has the power to spread darkness. As the darkness spreads, it begins to consume Hyrule, turning it into a "World of Darkness". FSA's Dark World represents the darkness in the process of consuming Hyrule. ALTTP'S Dark World represents the Sacred Realm that had been completely consumed by the darkness."

I can take some of these representatives across to your interpretation:

"The Dark World is made from the power of darkness that exists as a world in it's own right. As the power of darkness spreads to consume Hyrule (from Ganon as the source), the Dark World merges with Hyrule as part of that consumption. When Hyrule or the Sacred Realm is completely consumed by the darkness, the world becomes completely covered by the power of darkness, the Dark World."

I use a lot of representatives in this explanation because I think the whole concept of the Dark World is mostly metaphorical. Do you agree with this standpoint?