If I go to https://ell.meta.stackexchange.com/tags/voting/info , I get a "Propose Tag Wiki" button, but if I go to https://ell.stackexchange.com/tags/phrase-request/info , I don't get a button.
In both cases, the text is:
There is no tag wiki for this tag … yet!
Tag wikis help introduce newcomers to the tag. They contain an overview of the topic defined by the tag, along with guidelines on its usage.
All registered users may propose new tag wikis.
(Note that if you have less than 2000 reputation, your tag wiki will be peer reviewed before it is published.)
As far as I know, I'm a registered user.