usopp says they want to go to elbaf
They both want to meet the straw hats again and agree.
they agree to settle the fight and work out why theyre fighting later. its already determined its no longer a fight to the death.
later, they are still fighting when they learn their friends the straw hats made it to the new world and might actually make it to elbaf after all, so they settle the fight and go to meet them there.
it seems perfectly sensible. in this case (and probably a lot of others) its less that Oda isn't explaining it, and more like you never bothered to pay enough attention to catch how its already explained