Given that there's nothing forcing the Fed to unload these mortgages, the option of putting them on the market (thus driving commercial mortgage rates higher) seems like a policy lever that will be good to have, cooling real estate inflation selectively separate from the federal funds rate.
Driving rates higher won't cool inflation except by raising prices - which is inflation. They want to stifle the demand so as to match supply better, but when it's a supply shock and the United States is short something like 3 million houses, it seems a fairly punitive and misguided way to approach solving the problem.
There's still a supply shortage in building homes to deal with, but that'd at least solve a problem for a good chunk of folks.