It's a very good question, and the answer was conveniently left out of the blog post at hand. The reason art NFTs were created to begin with was because in the traditional art world, the people who make nearly all of the money are not the people who actually make the art. It is the art dealers and the art collectors who take the lion's share of the money.
The purpose of putting art in an NFT is to better balance the economics of art so that when the dealers and collectors continue to sell the art for increasingly higher prices, the original artist also gets some of the financial reward. This is especially important for young artists who are talented but are not yet able to sell their originals for a liveable wage or get any interest in a distributor to make prints.
A lot of people think NFTs are a waste of time and money, and I completely understand that paradigm, but NFTs are very important to the Artists who are trying to make a living wage from their passion. Ideally, this will contribute to even more imaginative art in the future.
I'd argue that Art NFTs actually share the values of open source software that were listed in the article, at least when it comes to improving "abundance, post-scarcity, universal access, and equality" for artists.
