It will cerify that battle as the biggest, baddest mofo's clash that could be made, highly anticipated fight. Best on all accounts best of the division in that time frame etc, etc. Will give more credibility to that clash, more hype. And could only be kept for a month without challenged against another top3 guy. Just saying. Is not really a 4th belt more of an achievement, one more thing to try and get when you got them all. Something like that.