A dedicated reference host is not required to be available to perform host profile tasks.
When you create a host profile, you extract the configuration information from a specified ESXi reference host. In previous releases, vSphere required that the reference host was available for certain Host Profiles tasks, such as editing, importing, and exporting. From vSphere 6.0 and later, a dedicated reference host is no longer required to be available to perform these tasks.
For host profile tasks that require a reference host, an ESXi host that is compatible to the host profile is assigned as the role of reference host.
Sometimes, a compatible host is not available to validate the host profile during these tasks. If you made small changes to the host profile that do not require validation, you can choose to skip the validation. If you choose to skip the host validation, a warning displays indicating that no valid reference host is associated with the profile. You can then proceed and complete the task.
Due to the introduction of this feature, users can no longer edit or change the reference host from the vSphere Web Client. The reference host selection occurs at runtime, without notifying users, in the vCenter Server for on-going tasks.