New RMA Caviar Black different specs and unable to change AAM settings

I just received a replacement RMA drive: WDC WD1002FAEX-00Y9A  Caviar Black and I noticed I am unable to change the AAM settings using HD Tune. I was able to do so before.  This drive is very noisy.  Info on HD Tune also shows no buffer size unlike my previous one. 

Any idea what’s going on with the new replacement drives?

Sorry mate, that’s not possible with the new drives…

fascinating. any idea why they made the change? do the new drives no longer have buffers too?