What little I remember from the 737MAX issue is that manufacturers are generally thought of as (and regulated as if they were) providing fully complete systems

What little I remember from the 737MAX issue is that manufacturers are generally thought of as (and regulated as if they were) providing fully complete systems and processes to airlines, so even for things like maintenance or day to day operations—while technically shared liability between the manufacture and airline—generally falls more on the manufacturer to ensure the safety and consistency of. That said, could just be a quirk of the reporting that we're seeing the manufacturer side of it and not the airline side here.