Atp his thinking must have been that he can take them while they’re in a recovery phase (7 days or no), maybe it’s that big of a difference maker. I feel like Shank’s intervention alongside his crew adds to this because obviously a force that defeated two yonko and a yonko crew should beat him under a normal circumstance. Also the classic “underrating the new school” thing.
He shows up 7 days later when he could've arrived there with WG right after the war ended if he truly cared about the advantage of them being exhausted