Although these stories sound cute.  I shudder when I think about my teen years when I stopped finishing sentences. My mind went on.  Many of friends just accepted it, but it created awful habits where I just didn't explain well.  I assumed people could see what I saw.
I *still* do that!  It drives DH absolutely crazy!  I have to consciously remember to verbally complete a thought and I'm sure people think I'm terribly flaky because I know I don't always remember.  Even my kids have taken to finishing my sentence because otherwise they'd never know if they understood me correctly, lol.