They are not scam, although they have no spreadsheets that provided to see our status, but bountyhive is doing there work well-done and honest, they have a lot of hunter that they are paying well. just obey the rules that they implemented and everything will be okay.
You are saying that there is no any spreadsheet means that there is no any transparency. If there is no transparency then there may be many faults and many things which the users will not like. If they want to continue their business with better results then they need to ensure the transparency in their platform. With it they may get many projects and will be famous more.