I have a friend who's a pathological lier and I've never seen any indication he's a psychopath. I've seen him go out of his way to help people many times and have never seen him try to manipulate others. Just because you have one condition doesn't mean you have the other.
Those are indications, not definite diagnosis. Think about it the way you think about symptoms of many other illnesses. They often start with „tiredness, lack of concentration, bad mood, weight change…”
So being a pathological lier means there’s something wrong. It might be psychopathy. It might be some consequence of anxiety. Or something else entirely.