Why is `org-element-affiliated-keywords' a var when `org-element--affiliated-re' is a const?

[Johan Tolö]

Dear all,

I want to add my own org-element affiliated keyword "REF" in order 
to provide a reference to some other part of an org mode document 
(or another document) for a link.
For example:

#+NAME: a-figure
#+REF: [[file:another_document.org]]
[[file:a-figure.png]]

I want to use `org-element-context' to get the link element and 
use `org-element-property' to get the `REF' property.
I tried changing `org-element-affiliated-keywords' in order to 
define my own keyword. This is never picked up by 
`org-element-context' since it uses `org-element--affiliated-re' 
which is defined as a const and thus is never updated to reflect 
the change to `org-element-affiliated-keywords'. The help text for 
`org-element--affiliated-re' even mentions changing 
`org-element-affiliated-keywords'.
Is this an oversight or am I trying to use this is a way that is 
not intended?
Johan

--
Johan