Philosophy students study study particular thinkers and the traditions in detail. And rightly so: theirs words are open to importantly varied interpretation. Students need to read read Plato because even today professors have non-trivial arguments about what he meant and how to apply the ideas.
So it is forgivably hard for philosophy to see beyond the western tradition it grew up in. But it is unforgivably dumb to try and justify the Euro-centrism by an by an false analogy to science.
I if a student is learning classical mechanics, she needn't read Principia Mathematica, and it doesn't matter what Newton was thinking when he wrote it. What matters is how you do physics today -- the various interpretations that physicists put on it can wait for some advanced course.