Please check the autocomplete search field; you will notice that the titles of posts from the secret space appear directly in the search suggestions. Who would want the names of secret documents to be visible in the search suggestions? Any user who is not logged in can view the names of document posts in the secret space. This means that all document name post in secret spaces are public, for anyone, whether it's a person or a search engine or a bot. Also the header image of the secret document is public in search suggestion so the claim that these spaces are secret is just a joke

Only those with access rights should be able to search for the document by name. Also, if the posts are secret, an encryption method should be used, just like for passwords. And only those with access rights can read them. That means a secret.

also the name of the document should not be written in the url address https://www.exemple.com/view-post/visible-name-of-the-secret-document it should be a meaningless string randomly generated.

browser console:

<div class="bx-def-unit-info flex flex-col pl-2">
      <div class="bx-def-ui-title">Visible name of the secret documentdiv>
      <div class="bx-def-ui-type bx-def-font-meta">postdiv>
</div>