That's true, but in this case I got a response from the head of trust and safety after I sent the phone recording, email + email headers, saying "This report is super robust and gives us a lot to look into. We are investigating this scammer now."

So they looked into it and eventually determined the root cause and then took action.

I don't know why you think acknowledgement of your report is concrete evidence that coinbase knew about their breach months before it was disclosed.