Grit, luck, and panache represent three different means by which heroes can gain access to the same heroic pool, using it to accomplish fantastic feats. For characters with a mix of grit, luck, and panache, they pool the resources together into a combined pool.
PDF and text export both show pool as the second class' bonus (grit) rather than the sum of the two (panache + grit). See attached PCG and TXT for usecase.
Should be triggering the shared pool.