Administrators don't see matches against the blacklist when creating pages.
When creating a page which does match a regex on the blacklist, administrators should see the same system message, but should additionally be informed that they can create the page anyways. Ideally, they should also be told what protection status the page will have once created. So if that BL entry has <noedit> it will be protected once created. If the entry has <noedit|autoconfirmed> it will be semiprotected. (Assuming I understand how this works correctly!)