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.
I've experienced joining a bounty where it has so many rules to follow and you should comply to each and every rule that is listed on it. I've finish a month and the bounty is finished but I missed one rule, that is to report (signature campaign needs a report) in that bounty thread. It is quite unusual but the manager demand it so I followed up and thanks he accepted. (At the moment still the tokens are not paid).