You know this discussion, for sure: Does a project manager need to be primarily a specialist in project management or in the professional field, and how much professional know how for the product to develop or implement does he need to lead the project successfully?
As an example: My background started ca. 30 years ago in a bank, followed by retail and consumer goods industry. Here I spent many years with topics like Category and Enterprise Resource Management (ERP). In the 20 years since I switched my focus from Industry Consulting to professional Project Management, I also added a lot of experience in Discrete Manufacturing, Machine and Plant Engineering, Telecommunication, Energy, multiple Services, Automotive, and at an Airline. From Strategic Branding and Business IT Strategy over M&A, Organizational Change, Digital Transformation and Process Optimization up to Development, Construction, Implementation, Commissioning, or After Sales and Customer Service I experienced kind of everything that could happen in project management. I even saw Civil Engineering in the Nuclear Industry.
My Experience: It doesn’t harm a project manager to have some insight and affinity with the project scope and the industry processes, which can be learnt fast with adequate deepth though. In the end his main tasks will be planning, coordination, communication, and leadership – the professional part is the experts’ task. His add value is in the efficiency and effectivity of the total.
Much more you as the project accountable manager should ask yourself: Are we looking for an experienced specialist in the professional topic or for an experienced in methods and leadership project manager, who ensures the project’s execution to plan? At which of the two we prefer sound education and skills? How much of his daily working time and attention should he put in the respective task, specifically: if trouble occurs in project, what may drown in case of conflict of time and objectives?
Conclusion: Your priorities are the answer. Both in one person in most cases leads to conflicts in time and objectives, and therefore to distress in projects.