Follow the storage
A backup service can run in a separate guest and still rely on the same storage platform as the workloads it protects. The separation is real at one layer and absent at another. The lab’s documented arrangement includes a PBS datastore backed by TrueNAS and another PBS instance with a separate datastore role. Understanding those relationships is more useful than counting backup-server icons.
What proves recovery?
A successful backup job is evidence of that job. Recovery also depends on access to the datastore, keys, configuration and a place to restore the guest. A topology diagram helps identify the questions. An actual restore supplies a different kind of evidence. Neither should silently stand in for the other.