There are a lot of reasons why a coin dumps after listing and it is not always because of distribution yo bounty hunters
Bounty tokens often only make up for 1-3% on average of the total project allocation and there are also a lot of other factors in play, like the exchange of listing, promotion, pre listing progress of the project etc.
I agree the bulk of the supply comes from investors and the team, some investors are dumping their coins when they saw that they are making a profit, they are making immediate return of investment and profit because of the bonus from being an early investors, some developers are giving 50% bonus from their pre sale