A client or contractor may develop it individually with each one, believing that it is more reliable than the current official schedule and/or the existing baseline.
Construction contractor can come up with a more aggressive version of the contractual schedule to create some form of relief time zones. It creates some form of time buffer zones by using earlier schedule plan dates. The sub-contractor then sign on a more optimistic schedule with the contractor.
The contractor hides the already optimistic phantom schedule for background update. At this point, and just on the contractor-subcontractor side alone, there are already four schedules at play and being maintained separately; i.e. 1) subcontract schedule, 2) subcontract phantom schedule, 3) contractor phantom schedule, and 4) contract schedule.
A recent technical article rightly stated the same thing, that one of the reasons why a phantom schedule is developed is “when the client no longer has any faith that the contractor’s contract schedule submittals are realistic (Beisler, S. & Zack, J., 2016.Cost Engineering. May\Jun 2016. p21).