KnockoutJs 1.3 beta. _destroy:false has same result on ui as _destroy:true

http://stackoverflow.com/questions/7679388/knockoutjs-1-3-beta-destroyfalse-has-same-result-on-ui-as-destroytrue

HTML

<script src="http://cloud.github.com/downloads/SteveSanderson/knockout/knockout-1.3.0beta.debug.js"></script>
<script src="https://raw.github.com/SteveSanderson/knockout.mapping/master/build/output/knockout.mapping-latest.debug.js"></script>
<div data-bind="foreach: ProductCategories">
    <div class="elementStyle">
        <div>Id: <strong data-bind="text: Id"></strong></div>
        <strong data-bind="text: Name"></strong>
        <div data-bind="if: Parent">
            Belongs to: <span data-bind="text: Parent"></span>
        </div>
        <button class="removeButton">Remove</button>
        <button class="sortButton">SortAll</button>
        <button class="renameButton">Rename</button>
    </div>
</div>

CSS

.elementStyle{background: skyblue; margin: 1px; padding: 4px;}

JavaScript

var model = [{"Id":1,"Name":"Bikes","Parent":null},
  {"Id":2,"Name":"Components","Parent":null,"_destroy":false},
  {"Id":3,"Name":"Clothing","Parent":null,"_destroy":false},
  {"Id":4,"Name":"Accessories","Parent":null},
  {"Id":5,"Name":"Mountain Bikes","Parent":1,"_destroy":true},
  {"Id":6,"Name":"Road Bikes","Parent":1,"_destroy":false},
  {"Id":7,"Name":"Touring Bikes","Parent":1,"_destroy":false},
  {"Id":8,"Name":"Handlebars","Parent":2,"_destroy":null}] ;

        var viewModel = {
            "ProductCategories": ko.mapping.fromJS(model)
        };
 
        ko.applyBindings(viewModel );