Why? He only beat a 320M bounty headliner
The bounties and threat level were equally attributed between between Luffy, Kid and Law over the defeat of 2 emperors
So considering his captain has the same bounty as Luffy, and he participated in the rooftop battle hype, i expect him to gain recognition for this as his right hand man.
Luffy is considered as a yonko because he has multiple commanders, with 3 above the billions mark. Kid should have at least one in that range, with Killer recognized as his right hand man, who participated in the rooftop battle, that ultimately led to the defeat of 2yonkos, most likely being used as the reason for him to cross the billions mark