I googled for an hour and still could not find a proper explanation for these 2 terms.

Is anyone able to explain why "respawn clicks" and "fogclicks" appear and are not always maphack related?

Because at the dota league i play 2 reports on this case have been rejected.
1 where another player clicks me while im still at fountain (minute 0) and another where another player clicks me in fog from time to time.
Both with the explanation that these clicks are not proof enough for a maphack. These clicks are caused by the WC3 engine.

Does WC3 really cause those clicks?
Is there any other way to proof a maphack than by finding those clicks?