It's highly unlikely Fender has a stamping plant or a plating facility. Or, a casting/machining center, for that matter. It would be pretty far outside their core competency. They're not metalworkers. They're woodworkers with some finishing/assembly capacity.
Not many manufacturers of anything complex are what's called "vertically integrated". That is, capable of fabricating/manufacturing goods from raw materials. The Bavarian Motor Works (BMW) and Ford Motor Company are a couple examples of those that were (but no longer). They would import iron ore, coal, raw rubber, cotton, sand, oil, etc., to make steel, glass, fabric, power, etc. and turn it into cars. Most manufacturers have some skill or process they're good at, and get others to do a wide variety of things they're not.
In the case of jack plates, why should Fender buy a massive multi-million dollar stamping line and dedicate it to making one or two things? The line would run out of things to do in the first week it ran, and all that investment would sit there rotting for the next year or two until they ran out of plates again.