Very few yacht building projects begin with fully developed engineering. Preliminary engineering, perhaps, but not fully developed, because few, if any buyers or owners are prepared to wait long enough before starting construction. It is, therefore, critical to assure that a sufficiently detailed and complete general specification has been developed and agreed to before the contract for a new project is signed.
Commitment to a detailed general specification presupposes that sufficient preliminary engineering has been done to judge whether the yacht can be built as represented during the initial development of the project. The general specification also provides the project consultant/manager, employed by the yacht's owner, with sufficient data to compare to previous builds and potentially identify anomalies that indicate potential obstacles to successfully executing the current project.
For example, you can pretty much tell from a detailed and complete general specification if the yard will be realistically employing a program of weight control and reduction for the project at hand. If not, and the basic details of the yacht call for a static displacement significantly less than other yacths of roughly the same size and type, you can conclude there are going to be problems with meeting performance projections.
Of course, if weight and performance are an issue, it would be better to have the engineering for the hull and other structure before making such a judgement. But the reality is that you usually won't have the full engineering package available at the inception of a project, and will have to settle for having the contracted general spec.