Please allow linked content to be added to the survey before it's published. The Survey123 Connect app is connected to the ArcGIS Enterprise Portal, so not sure why this section would limit the user to publish their survey before linking other content/items from Portal to it.
The reason is we have developed CI/CD pipelines that publish our surveys to ArcGIS Enterprise which allows us to keep the same item id throughout our environments so if the survey is used with hyperlinks in ArcGIS Field Maps, then these links will not be broken when the survey is republished, etc from an update/upgrade/etc.
Thanks