The thing is, Brannew was only explaining about the organization in that chapter.
Especially since Brannew & pretty much everyone knew that Buggy was the leader of Cross Guild looking at that poster, which the Strawhats, Kid & Law and even Crocodile as he is angry about it and shows it to Buggy - all recieved in the current time. They received info about CG like hours to at max a couple days before last chapters events.
In BB's instance also explains what I'm talking about, in the chapter where Yonko bounties were revealed we were merely shown BB's old bounty -something he most likely got when he became a Yonko- while a few days later during the Marine invasion, it looks like Teach has a new updated 4 Billion bounty even though he pretty much did nothing during that time and only raided Amazon Lily & kidnapped Koby.
That's what the hypothesis is about, that we're just shown Mihawk's, Buggy's & Crocodile's existing bounties: when Mihawk & Buggy were disbanded from Warlords & Crocodile's bounty from what he had done for 2 years and we aren't really seeing the updated Bounty of Cross Guild members in the previous chapter.
Besides, what kind of organization would have the leader having lesser bounty than someone who's seen as a subordinate? Which is why it makes much more sense for those bounties to be the ones released back when the Shichibukai were disbanded, it's just a hypothesis for now though there isn't really any concrete proof for that argument although it makes a lot of sense.
Yeah it pretty much said that they stood shoulder to shoulder once although I think the comment is more about what the Marines saw during Marineford when Shanks & Buggy interacted.
It's just Oda who revealed bounties in this upcoming chapter in flashback just to hype up battle of Hancock and BB which actually took place in Hancock's flashback.
Bro that's how these events took place, you can cross check that either by understanding the movements of plot or via Brannew :
1st - in Buggy's flashback, navy attacked and Crocodile came for his aid. Confirmed by Brannew. This thing took place first.
2nd - Buggy offered his crew and all the services for free to Crocodile. This includes news spread thing via flyers.
3rd - Crocodile contacted Mihawk which later tapped by marines as well and confirmed the alliance of Crocodile Mihawk and Buggy.
4th - Buggy's men spread fake flyer about new organization and its hot members after Crocodile's orders. This led to all misinformations.
5th - in current timeline when Buggy got dubbed as emperor via fake news, Mihawk and Crocodile started beating him up.
Now to clear everything about when bounties were issued, even if you remove TCB translation out of mistrust or even ignoring context in which Brannew release the bounties after giving all infos on CG and it's members. What would say about this, when Brannew details Buggy's bounty and came from Viz as well:
His intro and special achievements includes "he has the power to command these two other men" (Mihawk and Crocodile).
I hope this could clear up everything. There ain't anything which proves these bounties are before there formation of CG. If you don't want to believe even now than there's this facts for you as well :
- Since chapter 1053, when marines started issuing new bounties and the newspaper which got those details.
-First Goroseis getting angry on Luffy's "D" revelation, as well as G5 pic.
-Same newspaper displayed CG pictures along sides how Buggy got to become Yonko and a group picture of current emperors.
-Later Brannew detailing all of CG details and when they started joining and lastly when he issued all three members bounties, first he talked about there past deeds and how they come together and lastly in Buggy's bounty info, the powers to control these two monsters.
When in actuality its these two made Buggy rose to emperor position along with misinformations via Buggy's crew.
So marines issued these bounties after Luffy defeated Kaido, that is when the Goroseis were barking on marine personnel. Proof for that is again chapter 1058 when Buggy got noted together with Luffy as yonko.
It's just Oda who revealed bounties in this upcoming chapter is flashback just to hype up battle of Hancock and BB which actually took place in Hancock's flashback.
Also all the schibukais are getting boost due to there former affiliation with WG is might be true... what do you think ?