IMG_DNG reduse noise not work Camera Raw and Lightroom

I have done quite a lot of image processing and I have learned that a: there are several excellent raw processors, of which Adobe's is but one, and b: folks who refer to "Adobe Photoshop's" as though that was the name of the company who produced the app, may not know as much as they think. So it's always best to clarify, in my experience. I can also think of several raw processors with superior noise reduction to ACR - Dxo's Photolab for one. There is not a single camera maker who sees it as their job to devise Raw signatures that work for ACR, but instead see things quite the other way round. That's why there's always a lag between a camera being released and Raw supports added to ACR and other processors. But that said, as you seem to more interested in arguing and editorialising than providing information to assist with your issue, I wish you the best of luck.

What is "iMac Camera Raw"? Do you means Adobe's Camera Raw app? If so, best ask them.