Big banks do this to the juniors: pay them tons of money and work them to death. They have no problem finding talent. But I prefer companies find ways to make their employees lives not miserable instead of saying "here's some money for your misery, you may want to spend some of it on a good psychologist".
I am saying this as someone who has seen what working in oilsands does to people. Some people enjoy it, but some only stay for the money. They are extremely well-paid, extremely miserable, and never quit.
However I suspect we aren't talking about FAANG/unicorn-capable top talent here, hence the candidate applied to this job in the first place. I'd also be suspicious the candidate is ducking questions because they can't answer them. Unless it's just interview practice for them and a waste of time for the company anyway.
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.