Buying an item, and then selling it later, is not effectively renting. It's buying an item and then selling it later. The fact that they had the option not to sell and could choose to exercise it doesn't disappear when they do choose to sell it.
In this specific case I think it's completely wrong to say that people who sell back physical copies are effectively renters.
In this specific case I think it's completely wrong to say that people who sell back physical copies are effectively renters.