I can't say yes and no, because there must be some people who will immediately sell the coins they get from the bounty and there are also people who hold the coins they get from the bounty, besides that the allocation of the bounty is not too large from the total sales so even though the price dropped because the bounty hunter sold it cheaply but it doesn't have a huge influence at market price.
They dump it because the want a real money ( local tangible money ), they don't want to hold some useless altcoins specially if they see the future of the project. For me, as a bounty hunter... I have a lot of experience on that, so I see a lot of wasted project around the market. Even if I want to hodl it, there's a doubt on my head that this project never make any profitable income.
But it also a case to case basis, if I see the project is well prepared and has a lot of roadshow or seminar activity. It will be more interesting to have a share on their products. Just a few, but I can hold if that is deserving to.