This article has some shoddy logic. For the vast majority of drugs, the actual marginal manufacturing price per pill is essentially zero. That means that when the expired pills are thrown away and new pills are manufactured, there is no true economic loss. Rather, all that potentially happens is a transfer between the consumer and the manufacturer.
If pill prices were set by some external force, this could at least be an important society-wide transfer. But in fact, in equilibrium pill prices will be affected by the expected rate at which pills expire without being consumed. Even when manufactures have a monopoly, the manufacturer-surplus maximizing price is determined by the demand curve of the consumer which takes into account the expiry rate of pills. (If 10% of pills expire before I consume them, they are worth 10% less to me in expectation.)
Yes, I'm sure there are market model where expiry dates create net economic drag, or a net value transfer between manufacturer and consumer, but it's not even clear which direction the transfer goes. Such an analysis depends on the details of the world and how they are reflected in your model, which are completely absent in this article. Most importantly, the intuition that "letting $100 pills expire for no good reason must cause $100 of damage" is completely false when the marginal cost of manufacturing is low.
(There are exceptions where the marginal manufacturing process is expensive, but the article doesn't focus on these.)