He did not know LaTeX. Most of his papers probably were in LaTeX, as his students knew it. But I remember multiple papers he "authored" in Word, because that's what the student preferred.
I was in a top 10 school (in physics and engineering), and I can assert that the fraction of physics faculty who did not know TeX/LaTeX was at least a quarter, and could be as high as 50%.
All the major physics journals would accept Word submissions.
It's not at all unusual.
I have only met a few physicists who don't write papers in latex. They are all 65+ and generally work with younger scientists/grad students who prepare the paper in latex for final drafts and submissions.
No less than Donald Knuth in fact
This is already very tangential, but just for the benefit of anyone who may miss the humour and take the above comment seriously:
- re “couldn't afford professional typesetting”: Knuth was happy when Addison–Wesley approached him, specifically because he liked the high-quality typesetting of their books (like Thomas' Calculus) that he had used as a student. He was happy with the typesetting of the first editions of Vol 1 and 2, and only for the second edition, when the publishers moved from hot-metal typesetting to phototypesetting (that is, when the quality of the best achievable professional typesetting deteriorated), and he learned of the existence of digital typesetters, that he was motivated to come up with his own solution.
- re “couldn't be bothered to learn assembly language” — Knuth was approached by the publisher in the first place, because even as a student he had become a legendary compiler-writer (http://ed-thelen.org/comp-hist/B5000-AlgolRWaychoff.html#7) in multiple machine/assembly languages. In fact, the fictional “MIX” that he created was literally a “mix” of various then-existent machine languages (https://retrocomputing.stackexchange.com/questions/18117), some binary, some decimal (https://catonmat.net/donald-knuths-first-computer / https://ed-thelen.org/comp-hist/KnuthIBM650Appreciation.pdf), and MIX was introduced in the book with:
> There should be no hesitation about learning a new machine language; indeed, the author has found it not uncommon to be writing programs in a half dozen different machine languages during the same week! Everyone with more than a casual interest in computers will probably get to know several different machine languages…
Sometimes you have to collaborate outside of physics!