File Question - Cannot programmatically set a default value for the allowMultiple property

[JaneSjs]

Original issue

The following code doesn't change a default value for a File question in React: the Allow Multiple Files checkbox remains unchecked.

let prop = Serializer.getProperty("file", "allowMultiple");
prop.value = true;
prop.defaultValue = true;

Example.

In Knockout, the above code actually changes the Allow Multiple Files checkbox value:

However, the JSON schema comes with a wrong value:

{
     "type": "file",
     "name": "question1",
     "allowMultiple": false
}

Example.

jQuery: Example.