I have noticed when running scripts in the Management scripting console that jobs are updated immediately, even when there is no jop.save invoked.

Not sure if this is a deliberate change in the API, but can't find much documentation about this.
http://javadoc.jenkins-ci.org/hudson/model/Job.html#save%28%29

For instance:

Jenkins.instance.items.each { job ->
  println "--- $job.name"
  job.disabled=true
  //job.save() // this line is commented out, but all jobs are disabled
}

It may be my expectations, that not saving a job would mean no changes are made. I have encountered this when performing mass operation on SCM components and adding/updating build components.