They are different resources so they are cached separately. There is no standard that says that a cached response for https://foo.org/x can be used for a request to http://foo.org/x.

Those would be different URIs, and thus different URLs, and thus have different caching policies. URIs (and in turn URLs) must be consistent for caching to apply.

Consider:

  https://foo/a.txt !=  http://foo/a.txt

just like the obvious case of

  https://foo/b.txt != http://bar/c.txt

All of those are considered unique URIs.