Mac Installer unable to overlay AIR v24 SDK or later

From AIR 24 or later, it appears that the AIR SDK is not overlaid successfully resulting in a SDK that the installer says is packaged successfully, but it cannot be used with an IDE.
 
While i initially discovered this testing the 3.3.1 RC, I have since switched back to the v3.3 installer and experienced the same behaviour.
 
In my testing I am successfully able to build the 4.13 SDK with AIR 23 and earlier
 
Reading through the installer.log for the AIR 23 vs AIR 24 builds, the only difference i can see is that from v24 onwards, the AIR SDK is downloaded as a .dmg file rather than a .tbz2 file

 
i.e.
AIR 23 - Downloading Adobe AIR Runtime Kit for Mac from: http://airdownload.adobe.com/air/mac/download/23.0//AdobeAIRSDK.tbz2
 
AIR 24 - Downloading Adobe AIR Runtime Kit for Mac from: http://airdownload.adobe.com/air/mac/download/24.0//AdobeAIRSDK.dmg
 
This matches up with the switch in file extensions as configured in http://flex.apache.org/installer/sdk-installer-config-4.0.xml
 
For both cases however the installer then tries to untar the downloaded AIR SDK file, but this doesn't make sense for a .dmg file
 
i.e.
 
AIR23
 
air-setup-mac:
    [mkdir] Created directory /Users/phil/flex413air23-2/in/airsdk
     [move] Moving 1 file to /Users/phil/flex413air23-2/in/airsdk/AdobeAIRSDK.tbz2
Finished untaring: /Users/phil/flex413air23-2/in/airsdk/AdobeAIRSDK.tar
   [delete] Deleting file /Users/phil/flex413air23-2/airtar.properties
 
AIR24
 
air-setup-mac:
    [mkdir] Created directory /Users/phil/flex413air24-2/in/airsdk
     [move] Moving 1 file to /Users/phil/flex413air24-2/in/airsdk/AdobeAIRSDK.dmg
Finished untaring: /Users/phil/flex413air24-2/in/airsdk/AdobeAIRSDK.dmg
   [delete] Deleting file /Users/phil/flex413air24-2/airtar.properties
 
it appears that the installer is attempting untar the v24 AdobeAIRSDK.dmg file rather then mounting it to extract its contents.  This doesn't produce an error, and the installer proceeds to attempt to copy files that haven't been extracted, also without error.
 
This then results in the installer completing successfully, but without having actually overlaid the AIR SDK.