When the system does not have a flash player the code never runs through the killMojo method in FlexUnitMojo where the check for hasToStopBuildOnFlashPlayerFailure occurs. This is with the latest version 2.3.1.
The build simply ends with
[INFO] Client socket connection time out.
[INFO] Successfully open client socket.
[INFO] Client socket could not get I/O streams for localhost:11000.
[INFO] Closing client socket...
[INFO] Tests ended.