Every philosopher mentioned in the original article is Western, so I propose that we do limit ourselves Western philosophy, but if you want to argue in favor of a different proposal then I'd love to hear your reasoning.

Also, any philosopher who was also a mathematician and astronomer could have his or her contributions assigned to "mathematics" or "astronomy" which these days are whole other departments from philosophy, in whole other colleges. In that case, "philosophy" remains in the position of not having much to show for itself.