The latest chapter showed that Nami not only needs Zeus in order to put Ulti down, but she also needs to unlock CoO in order to land an attack on Ulti. The previous chapter showed that Usopp needs to unlock CoA to do actual damage to P1, so I think Oda is setting up the other SHs unlocking Haki. They’re gonna be the PK crew in like 2 major arcs from now, so they need to unlock Haki really soon. It’d make no sense for the PK crew, which only has 10 members, to have half its members lacking Haki when nobodies in the BMP, like Opera’s brothers, can use Haki.