I think you’re getting confused about who’s confused!
Let’s spell things out:
- The Ethernet standard uses isolating magnetics primarily for safety reasons
- The added benefit of common mode rejection means Ethernet is pretty good at rejecting noise
- Noise in the digital domain isn’t an issue; bits are faithfully transmitted and received
- A good quality DAC (or bridge) is designed to deal with noise and jitter at the input
The so-called tweaks are nothing but a go-faster stripe*. They may make someone happy, they may even deceive the those easily persuaded, but in the end they offer no measurable improvement.
*go-faster stripe in British. noun. informal. a decorative line, intended to be suggestive of high speed, on the bodywork of a car.