Yes, I experimented with this too -- and got it to work. But strangely, if
you leave out the

# eval: (org-babel-lob-ingest "./a.org")
# eval: (org-babel-lob-ingest "./b.org")

lines and do a regular `org-babel-lob-ingest` (or  C-c C-v i) on those two
files -- *it doesn't work. *Rather bizarre behavior, IMHO.

Anyway, the dream behavior for LOB would be to simply add your files to
your `org-babel-lob-files` in your Emacs init, start up an org file -- and
be able to simply use all the LOB files in your "live"
`org-babel-library-of-babel` list library.