Cannot delete an uneditable contentControl in Word Online

ScriptLab.yml

name: Delete a read-only content control
description: trying to demo a bug
host: WORD
api_set: {}
script:
  content: |
    var counter = 1;
    Word['run'](async function (context) {
      let doc = context.document;
      let endOfBodyRange = doc.body.getRange(Word.RangeLocation.end);

      let ccRange = endOfBodyRange.insertParagraph('', Word.InsertLocation.after);
      let ccParagraph = ccRange.insertParagraph("", Word.InsertLocation.after);
      await context.sync();
      //Find end after adding this and add another paragraph or else the insertion of the content control fails...
      endOfBodyRange = doc.body.getRange(Word.RangeLocation.end);
      var emptyParagraph = endOfBodyRange.insertParagraph("", Word.InsertLocation.after);

      let cc = ccParagraph.insertContentControl();
      cc.cannotDelete = false;
      cc.title = "Test Content Control";
      cc.tag = "EXAMPLE_TAG1";
      cc.cannotEdit = true;
      try {
        await context.sync();
        return fillContent(context, cc);
      } catch (e) {
        console.error("Failed to create content control during sync", e)
      }
    });



    async function fillContent(context, cc) {
      console.log("fillContent start")
      cc.cannotEdit = false;
      let entryPara = cc.insertParagraph("All work and no play makes Jack a dull boy.", Word.InsertLocation.end);
      cc.cannotEdit = true;
      try {
        await context.sync();
        console.log("fillContent completed")
      } catch (e) {
        console.error("fillContent: sync failed", e);
      }
    }
  language: typescript
template:
  content: |
    <button id="run" class="ms-Button">
        <span class="ms-Button-label">Run</span>
    </button>
  language: html
style:
  content: |-
    section.samples {
        margin-top: 20px;
    }

    section.samples .ms-Button, section.setup .ms-Button {
        display: block;
        margin-bottom: 5px;
        margin-left: 20px;
        min-width: 80px;
    }
  language: css
libraries: |
  https://appsforoffice.microsoft.com/lib/1/hosted/office.js
  @types/office-js

  office-ui-fabric-js@1.4.0/dist/css/fabric.min.css
  office-ui-fabric-js@1.4.0/dist/css/fabric.components.min.css

  core-js@2.4.1/client/core.min.js
  @types/core-js

  jquery@3.1.1
  @types/jquery@3.3.1