Fed has directly bought securities in every downturn that I know of. They bought MBS during 2007 recession. They are buying corporate paper right now directly. What they didn’t do was go bailout the mortgage REITs.
The Fed has not bought any corporate bonds yet. If you have some proof of that, please share your source. I work directly in this space, know everything that is going on and am unaware of any purchases so either I'm terrible at my job or you have some information no one else has.
You are correct. They have 700bb allocated for corporate bonds but no takers. They’ve dumped billions into MBSs and hundreds of millions into ETFs.