I think I know the issue. The latest Helm Chart version is still 0.8.2 which is coupled to JupyterHub 0.9.6 (versions-coupled-to-each-chart-release). shutdown_on_logout exists in JupyterHub 1.0.0.
From this post, we still don’t have newer version of Helm Chart coupled to JupyterHub 1.0.0