I don’t know why I’m so strangely bothered by it, but I have this lingering worry, and I really don’t want the great sky island to be one of the biggest island clusters. I get that the game wants to start out strong, but it would be a bummer to me if the game peaked early. What made BotW so cool is that it had this great opening area, but one that became completely dwarfed by the rest of the game.
I think the idea that the devs were going for is that the sky islands are generally smaller, more puzzle focused sections of the game. However, this is balanced out by the sheer number of them.
The Great Sky Island seems to be an exception to that rule because they needed a new place for the game to start in. The area acts both to introduce the concept of sky islands, and also to provide a reason for not being able to leave unprepared.
I'm going to call it now (it's already pretty much confirmed in my mind having looked closely at all of the sky islands shown both close up and in the distance), the Great Sky Island
will be the largest single sky island, cluster of sky islands, etc.
This fact doesn't bother me too much though because I'm sure this area was designed to act more like the Great Plateau, and less like the other sky islands. So while it may technically be the largest of them, there will be much more mechanically impressive islands.
EX: Stormy islands above Faron, various sky pillars, Hebra cyclone, Zora sky isles, etc.
Basically, treat the Great Sky Island as another Great Plateau that just so happens to be in the sky.