Totally tracks with what I've seen. The portal becomes a forcing function that slows down edge cases, which is most of what we actually build.
Better approach: portal as a search index over distributed docs, not the source of truth. Keep answers wherever they naturally live - repos, runbooks, team wikis - and make the portal just surface them fast.
We ditched centralized docs for tagged markdown files in the actual codebases. Took two weeks to set up. Paid for itself in the first month.