Nah, that should just be a gift you get when the actual Breakers game senses data from the Open Beta on your system. Basically, play the beta on whatever system you'll be getting the full game one, keep the beta on there until you have the full game and redeem said data, and then you'll have the Oolong keychain.
Based on what TobyS says, Xenoverse 2 seems to imply that whatever the item is will be 'more useful' once Breakers launches. I don't really have any guesses as to what that would be, but I'd imagine it's something more actively useful than a cosmetic item like a keychain.
What I'm also curious about is what may or may not carry over from the beta to the main game. I already played in the Closed Beta from a while back, and still had that application on my Switch; an update apparently changed that to the Open Beta, and carried over everything from that, including my avatar design, level, set skills, their levels, everything I'd unlocked, etc. I don't know that we'd be lucky enough that our levels and upgraded skills can be transferred into the real game, but maybe the stuff we've unlocked can?