It's NOT THAT simple, many times parts are subcontracted from the subcontractor!
IMO I work for a automotive subcontractor, We build the parts HERE, for the Factory over in Kentucky, but some sub assemblies we build with come from Japan, China, and France.
I cannot imagine what a electronic part would be like!

all those components, a shortage of just one value of a resistor that is needed can stop the whole show.
...even more so if it is a Service Item, lower priority as you are not shutting down million dollar factories, but putting customers on a backorder.
What happens many times is "projected production" and once in a while something does not sell, but more often than not, there is a greater demand(all those dudes in statistics and sales come up with these numbers)
So the Main business tells the subcontractors "we need 60 pcs per hour of this" and that is what the subcontractor goes with. When a line goes into service mode, for service orders, capacity is limited greatly since the "60 pcs per hour" line gets intergreated in another line and they just pump out "5 pcs per hour" and "8 pcs per hour of that, etc".
It is the Law that we provide ten years of service business after end of main production.