Undeclaring default namespace in XML 1.0

[Tomtec331]

I was switching to fast-xml-validator as the integrated validator of fast-xml-parser is marked as deprecated. When validating some of our xml data I came across an issue with namespace validation. A lot of the data we receive use xmlns="" to bring elements into global namespace. This is allowed according the XML 1.0 spec. See: https://www.w3.org/TR/xml-names/#defaulting (especially the last example).

Input (copied from w3 xml examples):

<?xml version='1.0'?>
<Beers>
  <!-- the default namespace inside tables is that of HTML -->
  <table xmlns='http://www.w3.org/1999/xhtml'>
    <th><td>Name</td><td>Origin</td><td>Description</td></th>
    <tr>
      <!-- no default namespace inside table cells -->
      <td><brandName xmlns="">Huntsman</brandName></td>
      <td><origin xmlns="">Bath, UK</origin></td>
      <td>
        <details xmlns=""><class>Bitter</class><hop>Fuggles</hop>
          <pro>Wonderful hop, light alcohol, good summer beer</pro>
          <con>Fragile; excessive variance pub to pub</con>
        </details>
      </td>
    </tr>
  </table>
</Beers>

Output (by using SyntaxValidator.validate(xml)):
ValidationError: Undeclaring the default namespace with xmlns="" is only permitted in XML 1.1 documents.

From my point of view this error should not occur.