Employment is maximized within the limitations of excessive inflation and vice versa. It is well established that a scarcity of workers has a direct, measurable effect on inflation. Therefore, one could conclude that it would be impossible for the Fedral Reserve to allow for a significant scarcity of workers, which is required for low wage workers to have meaningful leverage in negotiations, as it would voilate the mandate to maintain stable prices(inflation) as set forth in the Federal Reserve Act of 1913 [2]
To elaborate on this a bit. This it not so much a direct action of the Federal Reserve to create a scarcity of workers, as much as it is a result of a scarcity of workers causing inflation. That inflation would force the Fed to raise interest rates. Those rate hikes would slow the economy and would result in there no longer being a scarcity of workers.
The balance of the Federal Reserves two manadates, maximum employment and stable prices, results in about 4.25% unemployment(a slight scarcity) and 2% inflation(stable enough prices).[3] That is our current comporomise between stable prices and maximum employment.
[1] https://www.federalreserve.gov/faqs/money_12848.htm
[2] https://en.wikipedia.org/wiki/Federal_Reserve_Act
[3] https://www.chicagofed.org/research/dual-mandate/dual-mandat...