Senior Management is right.
In the same way you want to follow construction costs, billings and resources usage histograms as well as S-curves it makes sense for planning department and Senior Management to want to follow engineering costs, billings and resources usage histograms as well as S-curves.
Multiple WBS dictionaries will make it easier to define S-curve reports based on different WBS phases but what they are asking seems simple enough. Most probably your software should have a way to pre-define the multiple required s-curves. Just remember not to leave out projected values, budget/baseline and actual are not enough, you are equally concerned about projected final outcome versus budget/baseline.
S-curves are very simple, they represent cumulative time distribution of any combination of resources or costs. They will not tell you why, for this you must look at the schedule details but still they will provide a birds-eye view that Senior Management value.
I would like to know what you mean by Construction Engineering just to make sure I do not misunderstand you. I am interpreting it as more of a liaison between the design team and the construction team but perhaps shall include all work at the design office as well as at the work at the jobsite by the engineering team during construction phase. If the construction works delays this engineering work will be delayed, it is work linked to the progress of the construction phase.
For top management the whole portfolio matters, what happens at each individual job will have an impact on the portfolio, they got to mage their portfolio. The engineering/design team is relevant.
The following figure display some of the many S-curves that can be generated. Can be for individual jobs, resources, costs, or a combination. Can also include remaining work late cumulative curves, it is up to your needs.

It is precisely at time distributed data where CPM shines; after creating your S-Curve Diagrams and Tabular Reports Templates, at a few clicks of the mouse you shall be able to create the Graphic and Tabular Reports within your software as well as able to export to Excel equally easy.
BTW isn't Supervision work by the designer a deliverable even if under separate agreement? With regard to your statement "certification do not produce design deliverables and as such" does it means it is free of charge? No budget, no resources needed?
After design, when construction starts the design/engineering team provides much support for the construction to the extent deficient supervision can result in substantial project delays. On the other hand delayed construction will increase duration of supervision services. If your company provides both services then it must follow their status.
Best Regards,
Rafael