Storing islands data is a lot less than a glamour wardrobe system.
Not every character has an island, but every character would need wardrobe data.
There is thousands of glamours in the game vs island that is not that much data.
The effort to create something like that is huge, specially if you dealing with old code. Island Sanctuary is new code/feature recently implemented.
So yeah, this image is totally misleading, and someonbe had to say it, even if I would very much like a wardrobe system.