Sorting behavior changed between Adobe and Apache Flex SDK (?)

Hi,

I recently noticed some change in behavior between Apache and Adobe Flex SDK
(when working with our application which we shifted to Apache Flex SDK some
time back).

We have always seen that doing 'sort=null' stops any further sorting to a
collection of data (in Adobe's SDK). With Apache Flex SDK I've seen this
command makes no effect and sort mechanism is active.

To prove my query, I've attached herewith two links of one is using Adobe
Flex SDK (4.6) and Apache Flex SDK (4.11.0) the other. (I confirm this
behavior is exists in 4.12.1, too). Both are same application having a list
of unsorted data binding to a List component, and a button. When you hit the
button:

- Application sort the list
- Runs a command 'sort = null' to the collection
- Add a new entry at 0th index to the collection which starts with Z
character as initial

Results when used with Adobe Flex SDK:

- Application sort the list
- List shows data as - A, B, C, D
- null assigned to the collection.sort
- List added a new Z entry at 0th index and it shows as - Z, A, B, C, D

Results when used with Apache Flex SDK:

- Application sort the list
- List shows data as - A, B, C, D
- null assigned to the collection.sort
- List added a new Z entry at bottom and it shows as - A, B, C, D, Z

Is this something an intentional change with Apache Flex SDK or its an
issue. Please, suggest.

Thanks!

Apache Flex application link: http://www.datafilehost.com/d/0a36a69c
Adobe Flex application link: http://www.datafilehost.com/d/fdb76fad