I suspect there is a real relationship. General intelligence is a real phenomenon. Being smart at one task indicates, though does not guarantee, that you'll be smart at another task.

This is of course a different question than whether this test provides maximum predictiveness of future success. But it seems obvious to me that the test provides some information. It's really hard for a variable to be completely non-informative.

Lastly, I think it's important for us to not be too defensive. I sense, perhaps incorrectly, that sometimes we don't want to give value to tests we are bad at, because doing so would imply we aren't as good as feel we are.