Site Themes do not allow selecting different themes after setting a Confluence wide theme

Hello,

After setting up a Confluence wide Documentation theme (from Confluence Admin), with navigation appearing in left sidebar at each space, it is not possible to configure a space specific theme back to Default Theme (e.g. one space could have Default theme while others would have Documentation theme) so that the left sidebar would disappear on the corresponding space.

However, when Default Theme is set from Space Admin -> Look and Feel -> Themes, "Show or hide sidebar" option disappears from the corresponding space.

Confluence Admin -> Look and Feel -> Themes -> Help tips (bottom right) states:

"Space administrators may select a different theme for their spaces."

According to this, shouldn't it be possible to override the Confluence wide Documentation theme e.g. in one separate space?