When it comes to sending the notification (scatter_notifications I think?) the output (ie check result output) is taken from the notifications's "ref" field. And this ref field is taken from self here,. That would be shchedulingitem object...
And from what I observed and understood  so far - the schedulingitem object is not recreted everywhere near .. so the schedulingitem.output field is overwriten... at least during short periods (like between scheduler runs? i don't know exacty - i am not the owner of the code :)