The building in the scope is not the building on site
An upgrade changes the geography. Areas are hoarded off and not accessible, temporary routes carry traffic they were never designed for, and the finished areas that remain take the full load of the building. A scope written for the normal configuration describes a building that does not currently exist, and following it produces effort in the wrong places. Effort ends up spread across areas nobody can currently reach.
Revising it for the duration is straightforward and is worth doing properly. Areas out of use come out, temporary routes go in with a higher frequency, and the whole arrangement returns to normal when the project completes. Doing it as a documented variation rather than an informal adjustment means the cost is visible and the scope returns to its original state rather than staying wherever it drifted to.
