Yes their also evidence of a chain of events that occurred that has profound significance.
Oh and the reason Batman keeps his mouth shut on Booster trying to help Barbara; its called keeping ones mouth shut. The fact is the whole series is about Booster being a competent hero who needs to be seen as an idiot to the world to make sure he isn't just murdered in his sleep by time travelers; so it makes sense Bruce would keep this on the down low. Besides what good would it do anyways:
"Hey babs... remember Killing Joke, well turns out Booster Gold tried to stop that but time/space itself decided it had to happen."