I personally completely require documentation. Adding a feature may be beneficial in the short term, but not documenting it can create increasing maintenance burden in the long term. Every PR merged without docs slowly kills a project, even if it feels like it's better to merge initially. When this is repeated too many times, the project becomes increasingly difficult to maintain. Merging only PRs with docs is how you prevent a project from dying. Even the original author of the code will eventually forget why they chose to do something a certain way or what edge case they were covering at the time