some dump occurrences happen sometimes before bounty hunter gets token. and if we think, the allocation for bounty hunter is very low, almost all ICO allocates to bounty below 5%. I think it's not fair if bounty hunter is accused of being a price-dump maker.
Bounty hunters are never the cause of dumps and it is actually funny when I get to see a lot of people saying this.
About very tiny percentage of total tokens issued are dished out to bounty hunters which in most cases the tokens or coin would have been trading already before bounty participants get their share as you said, this is just some whale dump since they always end up getting huge bonuses anyway at the start of the ICO, so pushing the blame on hunters is actually uncalled for.