This is a good point. It's interesting to note, though, that the fed's balance sheet never really goes down and that today mortgage backed securities are still a huge part of the balance sheet and that the fed is still active in this area even though the MBS purchase program was ended.

We should also note that some of the companies will go bankrupt and the fed is doing little to qualify its loans. So it is not really a loan in the traditional sense (it is a low interest rate loaned handout).

Combining these two together, we have the potential to create a situation like Japan where the government is constantly managing the debt of some of the private sector. The cost on society for this can be much higher than the difference on interest rates shows.