Is this goal documented by the Department of War somewhere? Or are you guessing that there has to be a strategic reason for what seems quite wasteful. It sure seems like there's more efficient ways to achieve this goal.
Maybe there could be something like a weekend warriors but for machinists? One weekend a month, one week a year you build fighter jets. This does mean there needs to be private sector demand for those skillsets so the reservists have relevant day jobs.
Is this an official goal, or at attempt to handwave away the fact that we seem to waste trillions and decades to get anything done?
https://www.csis.org/analysis/why-us-defense-industrial-base...
Not really the point, but an idea that springs to mind is selling fighter jets to allied countries.