Spotlight on SQL Server Enterprise collects waits for all types of processes, even those that don’t have a SQL statement associated with them. Typically these are the system processes. There are also some circumstances where SQL Server doesn't include the SQL statement in the event for user processes. This is on the SQL Server side and is outside of Spotlight control.
The reason all types of processes are included is to make Wait Events more consistent with the Wait Statistics drill down which also includes everything.