That conclusion presupposes that rationality and empiricism are at odds or mutually incompatible somehow. Any rational position worth listening to, about any testable hypothesis, is hand in hand with empirical thinking.
https://plato.stanford.edu/entries/rationalism-empiricism/
(Note also how the context is French vs British, and the French basically lost with Napoleon, so the current "rationalists" seem to be more likely to be heirs to empiricism instead.)
That does compute with what I thought the "Rationalist" movement as covered by the article was about. I didn't peg them as pure a priori thinkers as you put it. I suppose my comment still holds, assuming the rationalist in this context refers to the version of "Rationalism" being discussed in the article as opposed to the traditional one.