I expect it depends on whether the bounty hunter is looking for immediate cash out, after the token/coin appears on exchanges, or if they see some value in the project and want to hold the token/coin for future use cases. Technically you might be able to classify them as investors considering that they own some small miniscule part of the platform/abilty to use said platform by helping them. Truly though you could then call anyone who received those tokens airdropped as investors which really doesn't mean much in terms of a traditional "investor" that puts forth their own currency believing that the platform will succeed.