I can think of two scenarios (could be more) where a night shift...

I can think of two scenarios (could be more) where a night shift is deployed to meet a practical completion date.

Scenario 1 - where the Contractor is behind schedule. Under Australian Standard contract documents (AS2124 or AS4000) there is a section called Liquated Damages. Liquated damages is not a penalty, but covers a situation where the Client (Core) incurs costs or losses (or lost revenue) from the delay. Usually is a "Sum" of $X/day (say calculated on Y tons/day of lost production @ $Z/ ton) . The contractor has to weigh up whether to incur this, or accept a reduced profit on the project by having to carry inceased costs, ie put on night shift. Is the contractor's call, as he carries the risk and costs of delay.

Scenario 2 - situation where Client (Core) may say to the contractor, I know we agreed on a completion date of say 30/3/2023, but can you tell me how and how much to bring forward the date to say 31/1 or 28/2. Contractor may comeback and say January no can do, but February with a night shift @ $6M can do. The ball is now in the Clients court.

From the announcement of $6M cost, my guess is Scenario 2. So it may seem as behind schedule but is at the behest of Core.

AIMHO. The dates are only there for clarity, not my guesses of new compltion dates.