It is not about that they were afraid to the bounty hunters to dump their token but because the purpose of the bounty here is to help the project raise awareness and especially the funds. If they will used btc and eth as a mode of payment  to the hunters they definitely can but, they ask for your help in terms of promotions. If they will pay in fiat also or major crypto then they should have pay ads markets for promotional rather using hunters. As for me as being oart of the dencoin tokens, as long as I am being payed of with the project im in, it will still be okay wether what maybe tje mode of paymnet they were to give.