Not sure where this is true but there are a lot of civilian wrench turners. There are whole sections with no military personel assigned even though they have the same career field.
True, but there are not nearly as many as there used to be. Most of those wrench turners were Wage Graders in the depots, and much of the depot work has been contracted out over the last few decades. The McClellan and Kelly depots were shuttered completely. Today, under the law, 50% of the depot maintenance can be outsourced to private industry. The Air Force has sought to increase that level due to increasing maintenance and modification needs. Increasingly, under a program called "Flexible Sustainment", the depot work is part of the original weapon system contract and is done by the weapon system's prime contractor.
At the same time, the desk-bound GS portion of the USAF civilians were cut less.