Setting `org-fontify-whole-heading-line' and `org-fontify-whole-block-delimiter-line' does not give a background color to the entire line in emacs 27. It works in 26.3 (although the latter variable is not present).

To reproduce, evaluate:

(require 'org)
(setq org-fontify-whole-heading-line t
      org-fontify-whole-block-delimiter-line t) ;; omit in emacs 26
(load-theme 'leuven t) ;; uses a colored background for org headings

Then open a simple org file, e.g.

* Hello world
** test
#+begin_src
#+end_src

In emacs 26.3, the entire heading line (and block delimiter) has a background color. In emacs 27, this is not the case.

See attached images.