It is true that HTTPS may impede some cacheable resources. Maybe HTTPS may be improved to allow transparent caching of _some_ content, but the security implications may be hard to predict and will require very careful implementation to not introduce new security issues with attacks on caches themselves (DNS system still has this problem AFAIK).
Instead, REST talks about a request being stateless and a response being stateless (i.e. sufficient on its own and not dependent on preceding or future communication between that client and server).
This is, again, done for the benefit of intermediaries, because intermediaries should not be forced to hold state in order to interpret REST communication. Every request, response should be sufficient on its own to be understood.
You have not demonstrated any flaws in it, REST says communication is stateless and cacheable except for acknowledging some select minority cases when it's not the case.
Turning the minority cases into the only way of communication nullifies most of the benefits of REST, because the whole rationale of the paper is lost. I.e. intelligent shared processing and caching by intermediaries.
I'm taking no stance on what "the reality is". I'm taking no side about which side is more correct. I'm stating what both sides want, and finding it curious they don't see the contradiction.