I think you and the article are referring to abstractions over different concerns.
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".
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".