For the first two albums, the album artist text field is recognised as containing a primary artist of that album. Thus it is sorted according to that artist’s last name - with Bach, CPE before Bach, JS.
Ok so far.
Now for the rest of the albums, the album artist field has not been recognised as containing a primary artist (see this post for a possible reason why) and so the field is taken purely as a text field and is sorted by first letters - “ca…” then “jo…”, and so these come after the “ba…” of the first two.