alt Hacker NewsAssembly is one example of manufacture, so that distinction isn't really the one you think it is. Output is tracked by value added, so the mythical "car comes missing a single bolt which gets added in Flint" doesn't really show up in the output numbers, if that's your worry.
Do you think that's a reasonable way to measure abd report manufacturing output?
Is laying our heads at the GDP idol's feet a reasonable measure of what these activities contribute to national welfare?