As a rule, such a procedure is attempted to reduce payments related to bounty companies!
Kyc for bounty hunters is not a fraud only if it is announced in advance. If after the campaign, it is fraud and extortion.
ElenaN is right, KYC is a method to cheat bounty hunters in large scale. Even if it's announced before the campaign all KYC documents can be lost if it's a scam. It's always dangerous to submit personal data and I recommend to boycott every bounty which requires KYC.