If you have a link for the Carin interview you are talking about, I'd definitely like to see it. I'm always open to new evidence. The comics themselves do not appear to indicate the kind of strict coherence and consistency with respect to the fine details of Superman's power set or power levels, over long periods, that you suggest. Nor have any of the writer and editor interviews, posts, letters, etc. that I have seen. But I could always be missing something and thus have been wrong.