Automatic refresh of nbdev_preview lost when using output-file on the frontmatter

Using `output-file` on the notebook frontmatter works great to specify a fixed URL. However, I lost the automatic refresh of the output of `nbdev_preview`.

Without `output-file`, any notebook changes saved get immediately reflected on `localhost:3000` when using `nbdev_preview`. This feature is lost when using `output-file`. Is this expected?