There's no aerospace grade for most of the components. It's either custom made for the most critical/unique components, hobbyist parts (who else needs 4" propellers), or cots that are designed for other applications.

Pretty much no one besides DJI has the scale for custom made, except on a few select components. Drones are still in their infancy, those companies are still trying to see if they have a business model and improving/creating technologies. You can't expect mature processes from this environment.