Earlier quoted context omitted.
Books, Music, Movies, TV, etc are all treated as fungible commodities due to the wide range of options. In much the same way that Meat and Coal have a wide range of quality and unique traits, but again the market has no problem dealing in bulk purchases. Granted, this often breaks down such as with the last mortgage crash but no abstraction is actually true.
What? No, nobody treats movies or music as fungible. Hence the extreme importance of A&R's, for example. And when you buy beef in bulk, that doesn't mean that they'll send you whatever meat they have on hand, nor is that what 'fungible' even means.
Electronic money, Stock etc are defined as Fungible because two people can exchange tokens of ownership in the same thing without impacting anything. The same is 'said' about crude oil and other physical thing even though they are not actually identical they are treated as such.
However, the same effect happens when company's own huge set's of IP. That IP is treated as an income stream and money does not care about it's origin. The reverse even happens with money. Coins as collectors items are independent from there nominal value.
For a back and forth example. Two Kids might trade 1's because the Serial Numbers of one of the bills contain 666 which lowers the value to one and increases it to another. Later if the bill is spent it could go though a hundred transactions where nobody cares about the SN.