Earlier quoted context omitted.
I agree. They just need to make this clear to him before he agrees to the job.
Job offers don't come with project guarantees. What next? A guaranteed table spot next to the window?
If your skillset is in huge demand, and a company needs you badly enough, they might just be willing to guarantee in writing what project you'd be working on - and maybe even give you a window seat, too.
Though if you're in demand, and want project guarantees, you'd probably be happier as a consultant - that way you're sort of always guaranteed to be working on the project you want, because completing that project is the entire reason the company hired you.