The client, if they had to ask an outside consultant to vet a candidate for them, must be a small business. They do not have enough work 5 full-time employees, one of whom works on design. The designer is the verification engineer and the project manager and the customer support person. I don't mean the person works 100 hour weeks. They will work the normal 40, but there won't be enough design work to do 40 hours of it per week.
If the candidate wanted to do one thing and one thing only, they won't find it in any small business. They should focus on applying to large companies. And the client should find someone who is fine with being a "full-stack" hardware engineer, instead of a hyper-focused professional.