Doesn't make sense given what we know of Yonko crew structure and bounties we have for reference. Flying Six are just under the Calamities, why would there be such a huge drop off when the lowest Calamity bounty is 1B? And guys who are just Headliners like Hawkins and Apoo are in the 300M range themselves? Going by Big Mom's crew, general members like Tamago and Pekoms have bounties of 300-400M. The closest to a Sweet Commander, Perospero, has a bounty of 700M. This would imply, at the very least, the strongest Tobi Roppo (probably Who's Who) should be in that range and the weakest should be at least above 350ish. If anything their bounties should skew higher since Kaido's crew's bounties have skewed higher than BM's crew's bounties. So Who's Who should be above 700M if the strongest non-commander in Big Mom's crew (Perospero) is 700M.
Hawkin's and Apoo were still exceptionally capable headliner's despite having bounties in the 300 mil range.
Like, I expect the flying six to all have high bounties, but I don't expect them to have bounties higher than guys like Kidd.
Nothing we've seen from them suggests that most or all of them would be in that ball park of bounty.
I guess we'll learn when its revealed, but I'd be surprised if more than 1 or 2 of them had bounties over 500 mil.