My understanding is that the Julia Petaflops run executed a Julia program per node, communicating via MPI. For some, that's probably obvious/expected for HPC; for others, it might not be considered "pure Julia".
It's my understanding that Julia aspires to join this group of languages if it is able to do so, which is why the Petaflops announcement was originally enticing to me, and then became somewhat less so once I learned that it was relying on MPI.