Earlier quoted context omitted.
The quantum superposition thing is just a cheeky metaphor for a sketchy-sounding accounting practice, I wouldn’t read too much into the wave-function collapse analogy.
It's a metaphor which makes it sound more complex than it is. All they are describing is that they have agreed to different royalty rates for different types of sale. I have zero doubt that the contracts will have very clear definitions of what counts as a 'sale' and what counts as 'licensing', but this article just pretends that it is highly ambiguous in order to make a strange analogy to quantum mechanics.
They get the rights management from licensing on the user side (no "giving away old albums to a friend" possible), while giving artists the lower cut as if it was a physical album sale with high distribution costs. It has nothing to do with digital vs physical sales, you could play the same trick with a CD sale.