Aren't they? Everyone in the dream seems self-aware and personified. Don't some monsters actually make a point later that they're trying to stop you from waking up the Wind Fish because they'll cease to exist if you do?
I mean, the game says it's the Wind Fish's dream. The Wind Fish itself seems to warp reality around it. The fanfiction writer in me would suggest that it effectively created a pocket dimension around itself. Unfortunately, the implication then becomes that waking up the Wind Fish effectively...
Didn't one of the Zelda compendiums actually state that Koholint Island was actually just some other dimension (which I still consider a lame cop-out that prevents world building)?