Symbolic linking for shared code-base for Drupal 8 not working but it did with Drupal 7

For Drupal 7 we were able to extract and have the code in a place like /var/www/drupal7/….. and then use “ln -s” to reference from the website document root most of the files and have own /sites/default… Thus updates in one place and multisites could not see files from another site because not in document root. Found someone had documented it here:
https://www.drupal.org/docs/7/multisite-drupal/secure-multi-site-setup-u…

A similar approach is not working for Drupal 8. It almost works but the upgrade took complains it can not edit the settings.php nor the files directory. If we redo with extracted code it is okay. seems like something in core needs to physically be in the document root and not linked?

Anyone else try this?

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/21/feed