This should not require a snippet, but it does. If a client setting is created and then deleted, its registry key remains and "effective date" value remains, and the setting itself is evaluated as still existing. Therefore, you must also check if the "value" value exists.
/*Use this:*/
exist (setting "BSHSI_RebootRequestSuppress" whose (exist value of it) of client)
/*Don't use this:*/
exist (setting "BSHSI_RebootRequestSuppress" of client)