I think you're being too uncharitable to the expert. It sounds like his point was that caching on disk is conceptually similar to caching in RAM, and that therefore, for purposes of prior art, you should probably list inventions that cached in this (similar) way. IOW, an engineer reviewing the literature should have included inventions that cached on disk if they were otherwise similar.
Remember, prior art is intended to demonstrate the extent to which your idea is new. It makes a big difference whether the inventor thought of caching at all vs whether they just used an existing caching scheme and swapped out the implementation for a faster one.
Posters on HN make a big deal about obvious patents being granted because someone took an existing invention and added "...on a computer/the internet". Well, it's a similar problem when someone takes an existing mechanism and says "... but on a faster storage medium instead".
Remember, prior art is intended to demonstrate the extent to which your idea is new. It makes a big difference whether the inventor thought of caching at all vs whether they just used an existing caching scheme and swapped out the implementation for a faster one.
Posters on HN make a big deal about obvious patents being granted because someone took an existing invention and added "...on a computer/the internet". Well, it's a similar problem when someone takes an existing mechanism and says "... but on a faster storage medium instead".