Looks like VMware change the USB driver method and only put vmkusb driver instead of XHCI/EHCI/UHCI/OHCI.
Vmware KB: Important information about the new ESXi 6.5 USB driver vmkusb, and the legacy USB drivers (2147650)
virtuallyghetto: No suitable disk was found when upgrading to ESXi 6.5 on USB?
Upgrade ESXi 6.0 to 6.5 from command line, if web traffic is OK with the host.
Something went amiss here: For one of the hosts (an old Dell PowerEdge) the update did not succeed. After reboot the host was back on 6.0.0. Looks like 6.5 was installed on a disk drive (and not the USB stick). After reboot, logs shows not evidence of the update (for the 6.0.0 installation on the USB stick).
If anybody is using the online update (as described below) to update an 6.0.0 on a (USB) stick - please let me know.