If bounty hunters know that a certain project is fake or scam they won't dare promote the project, the problem here is many bounty hunters are too lazy to do their own research on bounty projects before promoting, most do have jobs and make up their mind that it's a good project
Actually, my experience is quite different. When I actually used to have Telegram and Facebook, people would be messaging me their ref links and promising me it's still early to join. They would even say they know when to exit, so if we follow and invest NOW we can exit before it dumps.
What's this tell you? They know exactly it's a scam, and just want their rewards before the scam falls down. Why else would they dump at the earliest opportunity?