can.Model.findAll loads lists and mixes it with previously loaded

http://jsfiddle.net/qYdwR/643/


First, fiddle loads  and renders 5 todos with set attribute index (from 0.. 5)
Then click "Load New Todos" - with another fixture (that doesn't provide index attributes) we load new 10 todos, and render new list, so I would expect that: ALL of new todos would have index attribute undefined - but they do not, todos 1 to 4 have index attribute from old list.