You are right, those are both possibilities. Though, one of them has been explicitly presented by the author, and endorsed by Harry. I don't think we have much reason to doubt the canonical interpretation.

"SO THAT'S HOW THE COMED-TEA WORKS! Of course! The spell doesn't force funny events to happen, it just makes you feel an impulse to drink right before funny things are going to happen anyway! I'm such a fool, I should have realized when I felt the impulse to drink the Comed-Tea before Dumbledore's second speech, didn't drink it, and then choked on my own saliva instead - drinking the Comed-Tea doesn't cause the comedy, the comedy causes you to drink the Comed-Tea! I saw the two events were correlated and assumed the Comed-Tea had to be the cause and the comedy had to be the effect because I thought temporal order restrained causation and causal graphs had to be acyclic BUT IT ALL MAKES SENSE ONCE YOU DRAW THE CAUSAL ARROWS GOING BACKWARDS IN TIME!"