Yes, my observations are anecdotal at this time and my statements were meant to reflect my personal experience only.
I'm not following your logic. If a firmware update 100% corrects an underlying hardware problem, doesn't that hardware problem no longer exist? Isn't software written to accommodate the underlying hardware? Is the Cisco explanation mutually exclusive with a software patch that could correct the perceived hardware limitation? Is the architecture of the Cisco device relevant to the Denafrips DACs? Maybe an electrical/software engineer can help answer these questions.