Except if the Yonkou also has top CP0 agents and the literal Warlord replacements, then.....welp.
Especially considering the Navy always needs to have the stronger force, to neutralize the opposing side as swiftly as possible and with minimum casualties. They're not here to have a 1:1 Yonkou crew fight that's dumb.
In this case even dumber, only if the Seraphim are back on their side, will this start to make sense from a military perspective. And that's most likely why Saturn is here anyway.