When I saw this on Gigabyte boards back when the i7 4770k was current, I thought it was quite cool. However, I think it's largely unnecessary.
I suppose USB spec allows for minor modulation of voltage (it should be a constant and flat +5v DC) and other oddness, I mean a keyboard or mouse will probably work without noticeable errors.
If the motherboard is designed properly and a decent PSU is used, then all USB ports should be adequately clean. It then puts more onto the designer of the USB DAC to clean up the power coming in - which they should do anyway as they have no clue what the computer manufacturer is actually doing. So that would all become moot.
No isolated ground, so probably makes little difference, unless the DAC is really susceptible to voltage change.
I'll put the disclaimer that I am, by no measure, an electronics guru.
I would rather use galvanic isolation for USB or keep the host and device tethered with a common ground. From all the stuff I was reading there is a finite window in which the data lines will work, and that is in reference to the ground voltage - which should be the same between host and device. Having too high (or low/negative) voltage on the data lines, as seen by either device or host could cause irreparable damage.
I discovered that the D10 USB DAC will work without the common ground, after enumeration, but it's not really the proper long-term solution.
Galvanic isolation is different.
Also, using I2S from the DAC chip and galvanicly isolating that seems like a good solution in theory, but pricier.