Twenty years of people like my mom still not knowing what the hell that chunk of steel is!Why, exactly, did they have to do something other than "because old hard drive is old"?
If this were a change being proposed for Mac OS X 10.3 or earlier, then I might agree with you because the anatomically-correct internal hard-drive icon was always a terrible design (at least compared to common alternatives, including the icon used in Mac OS 9 or earlier). But now that icon has 20+ years of being ingrained as the standard internal hard-drive icon for Mac OS. Changing it now does nothing to help with making the OS more intuitive.
The icon should be either intuitive (which it never was, nobody knows what that stainless steel hunk of metal is) or accurate (which it hasn't been since the SSD era started).
If I could go back in time I'd try to convince them to make it a filing cabinet…