- Issue created by @tetatu
It is also illogical that on the "Content type" settings page, if "Preview before submitting" is set to "Required", once we have clicked the Preview button and returned to the editing interface, the Save button is already available on the editing page. After all, the essence of the "Required" setting is that the user checks the node on the Preview page after every change. The logical operation is: in the case of the "Required" setting, the Save button should never appear on the editing page, but only on the "Preview" page.
On your behalf I searched this issue queue for related items and found 📌 Add save dropbutton next to 'Back to content editing' link in node preview. Active but not much else about the oddity of in fact being able to save without previewing, which is what you rightly noticed. The behavior this issue cites dates back to decisions being made thirteen years ago in #1510544: Allow to preview content in an actual live environment → , which had its origin in controlled usability tests.
It could be that this was an oversight of the original design, this is a bug introduced some time in the last twelve or so years of development, or that people have moved editorial processes to workflows → , which is part of the core system.
Drupal's Slack workspace → is the best place for interactive discussions about product decisions and development direction.