As I have always emphasized, there are two kinds of Present Perfect:
ExA: He has lived in Japan before. (a finish)
ExB: He has lived in Hong Kong since 1900. (a continuity)
Trying to make decontextualised sentences do
your dance is inadvisable.
In ?"He lived in Japan before" , what period does the
before refer to? Before what?
In, "He has lived in Japan before", the
before clearly refers to before Now-the moment of speaking.
Past time is of course before Now, but think clearly about "before now" time and "past" time, the English verb distinguishes one from the other.
The past simple (remote form) refers to a point in time without any relation to any other point in time, the present perfect talks about time as looked at from the point Now - retrospective form.
Compare these two:
Joan is 34.
Joan is younger than me.
They are very similar to the contrast between the past simple and the present perfect. I'll let you figure out why.
And finally. I mean
finally:
I've seen this many times, Becky. (Looks back
OVER the past)
I've saw this many times, Becky. (Looks back
TO the past)
The hardest thing is to BE SURE why a speaker would use one form over another. That would be better interpreted in context. The only thing we have here are guesses, generalisations and hypotheses.