The issue, as outlined in the article, is that artists get different rates for whether a song was "sold" or "licensed" (with licensing giving a much higher percentage to the artist), and while services presented their sales as license agreements to the end customer, they presented them as sales to the artists, allowing the streaming service to restrict user rights while also not paying artists the much higher percentage.

There are of course different ways to interpret what a sale of a digital good is (as you note), but legally speaking with regard to the status quo, it seems like something large might be changing. Either end users might find they have a lot more rights (the ones they've traditionally had for purchased items), or artists will get a lot more money because they've been getting screwed for decades for licensed works, or possibly we'll see new legislation codifying the current status quo to protect the large media companies (because for some reason legislators often seem to think past ability to make money is a reason in itself to protect the method in which it was done, regardless of legality).