Documentation should be a first-class requirement for every feature of every software project.
If a feature is found to be missing (end-user or developer) docs, or the docs are missing some info, that’s a bug and should be treated as such: a ticket should be opened in the work-tracking system.
All docs start out insufficient and incorrect in some way — those are bugs. They can and should be fixed.
Let’s call it bug-driven documentation and let’s embrace it.