I think the young Le Guin just needed to build the mythology and cosmology to set up her fantasy world for the Earthsea stories. And hers isn't really so different from the cosmology/theology in some actual folklore. So she just set it up and went on telling the actual Sparrowhawk stories.
Then decades later she started to think of the implications of the chosen cosmology. They are cruel, but so are some of the actual folklore cosmologies. And then she invented this way to correct the cruel features in the fabric of her cosmology, and to write a very unique novel about it.
I don't see any hints in her pre-2001 Earthsea stories that she'd had intended this feature to be "fixed" later.
Then decades later she started to think of the implications of the chosen cosmology. They are cruel, but so are some of the actual folklore cosmologies. And then she invented this way to correct the cruel features in the fabric of her cosmology, and to write a very unique novel about it.
I don't see any hints in her pre-2001 Earthsea stories that she'd had intended this feature to be "fixed" later.