Hi.
Why isn't there a way to force the front-end builder to open in the correct template?
If the page is not assigned to the menu item, the system does not know anything about a specific template, so it opens in the default template.
This is the expected behavior and nothing can be fixed there.
Advice. Create a technical SP page, assign it to the technical (hidden) menu item with the desired template style. Create page layout with content there, then export/import result page layout to the article.