As already mentioned, use the HP customized image ISO for the installs/upgrades. As I understand it, the "offline bundles" are the HP tools and drivers (the pieces that HPE adds to the ESXi image to make it "customized" so it works best with their hardware)
You can import the offline bundle zip into Update Manager and use it to update HPE hosts already running the correct VMWare version. You can also use the offline bundle along with the VMWare ISO to build your own custom image.
Mike O.