Thanks Juri.
A better way to do that is to override the default value of
region-extract-function using add-function.
You could find some examples of add-function usages in
http://git.savannah.gnu.org/cgit/emacs.git/commit/?h=emacs-25&id=31f6e939334180add7bc11240343615a2e6350f6
and it seems to work fine as before, but with lesser lines of code! :)
So just to be clear, using add-function makes the region-extract-function tweaks a bit concise. But I would still need to update this if and when the region-extract-function default value changes in future. For instance, here I needed to have the "(not (eq delete 'bounds))" condition to match what was recently added to that var.
Kaushal