I think the confusion here is with the terminology you are using. An ESXi Host is the box running VMWare. An ESXi Guest is the VM running Windows, RHEL, CentOS, etc.
Are you trying to get patch information for the box running VMWare or the boxes running Windows, RHEL, and CentOS?
If it’s the vms running Windows, RHEL, and CentOS that you’re interested in then you will need to install the BigFix Agent on those.