JavaScript "this.metadata" is not return correct XMP metadata when PDF is locked by password.

This issue occurred on Adobe Acrobat and Adobe Reader 2019.021.20058. Is this bug? Or something specification is changed? 

*It's not occurred on 2019.021.20056 and lower. 

You can reproduce this issue by below.

1. Open this PDF file with Adobe Acrobat. 

  https://krwww.s3-ap-northeast-1.amazonaws.com/support/adobe/sample.pdf

  *It's same with attachment file "sample.pdf".

2. Open JavaScript Debugger and execute "this.metadata". It return correct result below. This is same XMP metadata in the PDF file. 

<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 5.6-c016 91.163616, 2018/10/29-16:58:49        ">
 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description rdf:about=""
    xmlns:pdf="http://ns.adobe.com/pdf/1.3/"
    xmlns:xmp="http://ns.adobe.com/xap/1.0/"
    xmlns:xmpMM="http://ns.adobe.com/xap/1.0/mm/"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
   pdf:Producer="Acrobat Distiller 4.0 for Windows"
   pdf:Keywords="Tiger, Sample File, PDF, &#xD;&#xA;Other keywords..."
   xmp:ModifyDate="2019-12-12T09:43:11+09:00"
   xmp:CreateDate="2001-02-07T12:43:33Z"
   xmp:MetadataDate="2019-12-12T09:43:11+09:00"
   xmpMM:DocumentID="uuid:e078b573-fbb6-4975-ac4e-7ad8f5315af3"
   xmpMM:InstanceID="uuid:85cb8a4b-48ea-4f72-92e8-78b01658b87f"
   dc:format="application/pdf">
   <dc:title>
    <rdf:Alt>
     <rdf:li xml:lang="x-default">Tiger</rdf:li>
    </rdf:Alt>
   </dc:title>
   <dc:description>
    <rdf:Alt>
     <rdf:li xml:lang="x-default">Sample PDF</rdf:li>
    </rdf:Alt>
   </dc:description>
   <dc:creator>
    <rdf:Seq>
     <rdf:li>Unknown</rdf:li>
    </rdf:Seq>
   </dc:creator>
   <dc:subject>
    <rdf:Bag>
     <rdf:li>Tiger</rdf:li>
     <rdf:li>Sample File</rdf:li>
     <rdf:li>PDF</rdf:li>
     <rdf:li>Other keywords...</rdf:li>
    </rdf:Bag>
   </dc:subject>
  </rdf:Description>
 </rdf:RDF>
</x:xmpmeta>

3. Lock this PDF by password and reopen it. 

  *Any password setting is OK. It's no influence for this issue.

   You can downlod it from below. Owner password is "test".

   https://krwww.s3-ap-northeast-1.amazonaws.com/support/adobe/sample-locked.pdf  

   *It's same with attachment file "sample-locked.pdf".

4. Open JavaScript Debugger and execute "this.metadata" again. It should same result with step 2 but return below. It is different with actual XMP metadata in the PDF file. It seems Adobe Reader regenerate this XMP metadata from Info dictionary. So some metadata are missing.  

<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 5.6-c016 91.163616, 2018/10/29-16:58:49        ">
 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description rdf:about=""
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:xmp="http://ns.adobe.com/xap/1.0/"
    xmlns:pdf="http://ns.adobe.com/pdf/1.3/"
   xmp:CreateDate="2001-02-07T12:43:33Z"
   xmp:ModifyDate="2019-12-12T09:44:29+09:00"
   pdf:Keywords="Tiger, Sample File, PDF, &#xD;&#xA;Other keywords..."
   pdf:Producer="Acrobat Distiller 4.0 for Windows">
   <dc:creator>
    <rdf:Seq>
     <rdf:li>Unknown</rdf:li>
    </rdf:Seq>
   </dc:creator>
   <dc:description>
    <rdf:Alt>
     <rdf:li xml:lang="x-default">Sample PDF</rdf:li>
    </rdf:Alt>
   </dc:description>
   <dc:title>
    <rdf:Alt>
     <rdf:li xml:lang="x-default">Tiger</rdf:li>
    </rdf:Alt>
   </dc:title>
  </rdf:Description>
 </rdf:RDF>
</x:xmpmeta>