It all has to do with windows authentication.
Typically, load is generated from one client machine which means that each virtual user will authenticate themselves as the user running the load test (if windows authentication is used). If session recovery is enabled, all simulated users will recover and use the same session. This will in effect mean that they invalidates each others state when new actions and selections are performed in the document.
As the load test aims to simulate unique sessions, by checking ProhibitSessionRecovery all virtual users will have their own session and state even though the load is generated from one source machine.
If the virtual users are authenticated in a different way, e.g. header authentication, it does not matter whether ProhibitSessionRecovery is checked or not as long as each userid is used only once during the load test.