> You can also re-discover the dates by doing your own historical research
My point was that you can put a mathematician in a closed room with only pencil and paper, and they could redevelop an entire theory if needed. A historian in the same position would be unable to do any work -- they need primary sources. I went with your "learning lists of dates" as a stand-in, since, like primary sources, you can't derive dates from scratch.
Sure, history has a "how" of research methods, but the research products must rest on the "what." Mathematics is almost entirely "how." The "what" for a mathematician is mainly knowing what's been done and what needs doing, for the purposes of directing research and giving attribution.
Also, I am pretty sure G.C. Rota was being somewhat facetious in quite a lot of the article. These are "lessons of an MIT education." Lessons aren't necessarily truth.