Ofcourse it is!
Nowadays, I notice most of bounties have strick rules, making bounties more organize and I like that Bounty Manager requesting Proof of Authentication to limit scammer .
It's been one of major mistakes of bounty hunter like me not to read rules and requirements of each bounties ending up not getting stakes so it's very important to read and understand each rules to ensure that we're doing the right thing and not wasting our time and effort.
For me yes! We need to be strict in bounty campaigns. Why? so that the bounty hunters will be disciplined and well trained in doing their work in bounty campaigns. I agree to you to do the "Proof of Authentication" to limit the scammers so that, me as a bounty hunter will not waste my time in doing bounty campaigns.