If these images were stored on the blockchain, would that make a difference?
I'm really puzzled about why aren't they publishing a low-res copy of the image, and sending the buyer of the NFT the unpublished high-res version. That way only the buyer (and the artist) would have that file, and by keeping it secret they could make it rare, albeit not necessarily valuable.
And because the marks think that they're gonna get rich off owning a blockchain pog with a link to a monkey jpeg, the art doesn't have to be good, either.
A lot of projects actually do assign a license to the sale.