Spam instead of Junk folder

[Robert Moskowitz]

Traditionally I have used 'Spam' as the folder name for all those emails 
that get tagged as, well Spam.

But it seems that the standard is now 'Junk' as from 15-mailboxes.conf

     # Space separated list of IMAP SPECIAL-USE attributes as specified by
     # RFC 6154: \All \Archive \Drafts \Flagged \Junk \Sent \Trash
     #special_use =


If I have in local.conf

# 15-mailboxes.conf

namespace inbox {
   mailbox Spam {
     special_use = \Junk
   }
}

This would auto make Spam, but:

Would Junk (and all the others specified in 15-mailboxes.conf) still get 
created?

What actually controls which folders get created?