I listened to Unknown Player and he's being pretty open in saying that this one seems a whole lot different to other invitations. Others had NDAs on them and it was purely to play the DLC or whatever it is.
They'll still play DLC but admittedly he even says they won't be able to change that piece of development as its already done. Its the Summer and beyond changes that they can actively help steer Bungie in the right direction. The 3/4 youtubers I watch for Destiny, I agree with their potential changes 99% of the time.
I won't deny its good PR move, but on this occasion the value added they get back from this will be heard and hopefully one day seen by the entire Destiny community.