FSI Server is an image processing application and therefore usually has higher resource requirements than an ordinary webserver. The benchmark can help estimating the hardwares performance. On virtualized systems where the host system is not under your control this is a problem as there is no way of knowing what other processes are running or might be running on the hardware in parallel in the future. Running the benchmark in such an environment will not produce results of any significance. Running FSI Server on shared hardware is therefore not recommended.
If virtualization is for administrative purposes only and you have full control over the host system and the resources assigned to the guest system, then the benchmark can be used as stated and the results can be interpreted accordingly.