The article is cherry-picking for sensationalism. Those aren't representative, obviously. And the "there's no rhyme or reason" is the author's (entirely unsupported) opinion, not a fact.

Amazon is a for-profit business. It's not intentionally dumping MacBooks it can resell profitably.

Obviously neither of us knows in this particular circumstance, but one would assume they were damaged enough to not be resellable, that a mistake was made somewhere, or a third-party seller using FBA requested them disposed of for some reason (e.g. an ancient used model there was no more demand for).