This is not the only example of well curated image-tag pairs, especially in artistic circles. It's just that most of them are not CC.
Danbooru is only one such example of well curated tagging and if we ignore copyright there are far more examples. These example just serve as evidence that refining poor labeling is not outside of the relm of possibility as you suggested.
An example, an image is tagged: kanna_kamui, kimono and torhu_(maiddragon), who has the kimono? Kanna, Torhu or both? It cannot be known, but with natural language it is possible to describe who is wearing what.
Edit: an experiment comparing tags/BOW vs natural language sequences in image generation tasks would be interesting to see.
Citation, please?
I think you mean "the developers of this technology do not want to pay to have hundreds of millions of images labeled".
Unstable Diffusion is also doing their captioning like how I mentioned, with groups of volunteers as well as hired individuals.
They seem to have created a much smaller dataset than LAION's, it would not work to train a generative model on such a small amount of images (obviously the images here do not have a single domain).