I'm afraid that I know nothing of Boeing - although others here certainly do.
But, in general the term "project pilot" is applied throughout the test flying community to apply to the senior test pilot on a particular project. That is, they are responsible for the conduct of all TP related activities on that particular project - although it's not uncommon that also flying on the project will be people who are senior to that pilot (but subordinate on particular project test-flying issues).
Having said that, I suspect from your post that your question is possibly a bit deeper than you are letting on - perhaps you'd elaborate a little?
G