The concern you're talking about is about the actual access to the data. My understanding of the article is that it's about how caching algorithms can abstract the concern of minimising retrieval cost.
So in some ways you're coming at it from opposite directions. You're talking about a prior of "disk by default" and saying that a good abstraction lets you insert cache layers above that, whereas for the author the base case is "manually managing the layers of storage".
* Got paid a referral fee if I signed up
* Owned shares in the company
* Even was roommates with the founders/CEO but failed to mention it
I would trust that person less going forward.
If you want to be perceived as trustworthy, then you shouldn't say things that you have a hidden interest in saying.