The underlying helper method for the SiteHelper.StandardDocumentQuery is this:
public static List<T> StandardDocumentQuery<T>(string path = "/", int nestingLevel = 1, PathTypeEnum pathTypeEnum = PathTypeEnum.Children) where T : TreeNode, new()
I don't know if that is helpful. I've been trying to get some more information using the SQl Server profiler but its not proving very fruitful. I write to the event log right after the call and it returns zero as a count in the trace.