How they create Spam folder?

NextCloud 22
Mail App 1.10.2
IMAP server Dovecot 2.3.15

In this article 5 open source webmail clients for browser-based email | Opensource.com in NextCloud Mail app screenshot there is a Spam folder.
How they create it?

gmail-nextcloud

All that I can get only two ‘Junk’ folders.
Can’t create Spam folder as submailbox.
App with any problem allows to create submailbox with any name instead of ‘Spam’.
With this name it throws no error, just did’t create anything.
Also can’t rename existing Junk folder to Spam.

So how they create Spam folder on those screenshot?

Part of Mailbox Dovecot config

 mailbox Spam {
    auto = subscribe
    special_use = \Junk
    autoexpunge = 7d
 }

 mailbox Junk {
    auto = subscribe
    special_use = \Junk
    autoexpunge = 7d
 }

Well you can create the mailbox. And Mail will try to guess it’s special use. If the mailbox has \Junk set by the server then it will show as a special spam mailbox. Nevertheless there currently is no way of setting a spam mailbox. This is missing, as we just found out the other week: Move spam messages to spam mailbox · Issue #5326 · nextcloud/mail · GitHub