Not necessarily. The dump isn't always because of bounty hunters dumping their percentage off in an exchange.
It might also mean early investors getting out of the scene after knowing certain flaws in an ICO or losing credibility thereafter.
Some ICOs lock tokens in 2 month for bounty campains. It is unfair. Bounty hunter do invite, PR,... for projects but they take less profit than investor.
It all boils down to the exact ICO in the first place.
If you don't like their terms, then don't apply. Simple.