Whilst triggering a MultiJob, one wishes to determine on what node the Job will actually run on, and this may be quite complex when you have 3 pahses with 2 jobs in them and you want to control what will run where.

You could use the "Tie this job to node" which comes in Jeknins out of the box, but then you loose the flexibility of Multi Job which basically can take you from Dev => QA => PROD where all that changes is the nodes which your process is running on.