The tags page in Meta sometimes shows the usage guidance of the tag and sometimes doesn't. For example, in the screenshot below, the usage guidance for the discussion tag is shown ("designed to solicit [...]") and that for the tags tag isn't. The tags tag currently does not have any usage guidance, so it is understandable that it isn't shown. But, say, the feature-request tag currently has usage guidance and yet it isn't displayed.
Is this a bug?
Yes, this is a known bug: see The initial default version of the tag-excerpt not shown on the tags page on Meta SE.
Briefly, the required tags and moderator tags come with pre-filled wikis and wiki excerpts, but the excerpts are not displayed on the tags page. One can submit an "edit" by just saving the default texts of the wikis and excerpts and then the excerpts will be displayed normally after the edits are approved.
I went ahead and saved the default texts as suggested edits on all the tags affected by this bug (except status-review since it appears that it already has a pending suggested edit.)
Update: The suggested edits on all the tags affected by the bug have been approved, so the excerpts are now visible normally.
