Multiple socalled "unrelated" failures do happen often, usually because fire or uncontained failures don't limit themselves to one place in the aeroplane. Fire spreads and destroys everything on its path, flying pieces of metal as well. And you cannot simply "neglect" that possibility. Things like these should be trained, but they should be "training" and not checking. Management of checklists, making priorities, personal behaviour, CRM,... these are vital lessons to SURVIVE in those cases (consider UA 232 in Sioux as an example) because all of these situations are all different.