The valuePropertyName property doesn't work in a Dynamic Matrix

[JaneSjs]

I use the valuePropertyName to populate a Dynamic Matrix with selected Checkbox items. However, the Expression column doesn't display the selected item's value. If I create a Dynamic Panel instead, it works as expected.
View Demo

{
 "logoPosition": "right",
 "pages": [
  {
   "name": "page1",
   "elements": [
    {
     "type": "checkbox",
     "name": "myTest",
     "title": " ",
     "hideNumber": true,
     "choices": [
      "Item 1",
      "Item 2",
      "Item 3",
      "Item 4",
      "Item 5"
     ],
     "valuePropertyName": "testItem"
    },
    {
     "type": "matrixdynamic",
     "name": "question3",
     "valueName": "myTest",
     "columns": [
      {
       "name": "Column 1",
       "cellType": "expression",
       "expression": "{row.testItem}"
      },
      {
       "name": "Column 2"
      },
      {
       "name": "Column 3"
      }
     ],
     "choices": [
      1,
      2,
      3,
      4,
      5
     ]
    },
    {
     "type": "paneldynamic",
     "name": "question1",
     "valueName": "myTest",
     "templateElements": [
      {
       "type": "expression",
       "name": "question2",
       "expression": "{panel.testItem}"
      }
     ]
    }
   ]
  }
 ]
}