Short answer

Keep the administrative effort as low as possible: If you accord details access permissions, you create administrative overhead.

Longer answer

Usually, all stakeholders can read and write the documentation. Some cases justify exceptions from this rule:

• For large teams, you should modularize your documentation and restrict write-access to certain parts, to avoid accidental changes.

• You might differentiate (short-term) project and (long-term) system documentation. Everybody can write in project documentation, only few people might modify system documentation.
• In case of regulated documentation, you might need detailed permissions (and access logs) to avoid manipulation.