I think this chapter proves that the Marines view Bounties as a means to not only control pirates by making them feel threatened/hunted, but also to control narratives.
Why would the WG not want Luffy to have a huge bounty? Simple, they're scared of Joy Boy, and want to downplay him as much as possible.
"Law/Kid/Luffy took over Wano by defeating Kaido/Big Mom" is totally different than "Mugiwara Luffy, possessing the most dangerous Devil Fruit in the world, defeated Kaido in 1v1 combat to liberate the land of Wano."
The WG does NOT want its people to start worshipping the idea of this "Joy Boy" liberating countries by defeating despots... because, they're literally worse than Kaido.