Bayes Theorem is independently (exchangeably?) proven again!

Back in 1763 the World Wide Web wasn't yet fully developed [we only
had gophers for communication back then], so I can accept that not
everybody has heard of my Theorem, nowadays kindly called Bayes'
Theorem by those in the know.

But even now, it seems, some poor souls have only got up to 17th
century mathematics, such as calculus and the Bernoulli distribution,
but ultra-modern 18th century stuff like my Theorem. And so these antediluvians have had to prove it all over again.

Seriously. And then they go on to call it the "exact method" (as
opposed to the frequentist "method" which assumes too much and answers
too little, but is clearly much more famous than my apparently
old-fashioned Theorem), wondering

It is not clear why the exact method isn’t mentioned in
most textbooks or, indeed, why it isn’t universally used instead of
the standard method. Apparently the exact method is not well
known.

Indeed not.

[A tip of the hat to Xi'an
(a.k.a. Christian P. Robert) for the generous promulgation of this
delightful finding]