The point, more broadly, is that these are loans with a quick expiry baked in. The money comes into and poofs out of existence on a relatively short timescale (ranging from overnight to a couple of weeks); we aren't going to see an extra ~$3T in circulation. They're providing lubrication in the repo markets, they aren't just shoveling cash into the banks' vaults.
Most people misunderstand this point when discussing repo operations, so it's worth emphasizing.
Most people misunderstand this point when discussing repo operations, so it's worth emphasizing.