Your clarification makes sense - a PhD advisor with a bit of NSF or other grant money would likely only fund a grad student to work on a problem that has a reasonable likelihood of generating some concrete, positive, and publishable results. This typically means an incremental result on a problem of interest to the research community.

That having been said, an accepted proof that P != NP would result in a Turing award and an additional $1M for solving one of the seven Millenium Prizes. This has been an open problem for decades, and it is a problem of enormous importance and visibility.