>>the convention in the 1940s to include titles with people's names. That's still the convention in AE today
That's actually not true in my experience, at least not in the context of academic writing, which is what this seems to be, as opposed to correspondence.
There are one or two US newspapers, the best-known one being the New York Times, whose house style persists in using the titles Mr., Mrs., and Ms. with the names of well-known people, but it's a self-consciously traditionalist convention that now largely comes across as old-fashioned. (And I'm not sure that's actually that much different in BE -- it's the kind of style rule that wouldn't surprise me in, say, the Times or the Telegraph, but that I wouldn't expect from the Guardian.)
>>We don't generally stick a full stop after Prof
I thought the rule was that in BE you were supposed to, unlike with Mr and Mrs, which end with the last letter of the full-length word, as L.G. explained.
But anyway, there are a dozen or more threads in the archive on AE/BE punctuation differences, with links to usage guides, so we don't need to revisit the punctuation part here.
I have no particular opinion about the question in the original post either, beyond agreeing that 'Mr.' in this kind of context just comes across as dated or old-fashioned now, though it was probably more typical 60 or 70 years back (and perhaps still more so 100 or 150 years ago). The question seems still to be open whether the same may have been true in German texts from a similar period.