So sidebar search bars do not count in the template of the outlined address bars.
Only non-toolbar "address bars" count. Sidebar toolbar partitioning has been added in Big Sur, but though yet it has already been added, applications such as Safari and Finder most notably.
So in essence, what Orion needs is implementation of the UI framework regarding the sidebar toolbar whilst maintaining the ability to show it only on the start page, which could be done with an animation unlike Apple which simply just removed the option to show the sidebar automatically only on the start page. The start page just like a library should have an option to only show on the start page and clear itself for the content to show to avoid distraction. Although the sidebar usages of both Safari and Orion are both different.