Well that's kind of the point, isn't it?
I don't buy that logic though. By that reasoning, we should ditch all outboard phono stages, separate preamps/amps, DACs, and subwoofers, because that's a lot of extra interconnects, digital cables, power cables, capacitors, subwoofer amps and power supplies affecting the signal. You don't listen to a signal, you listen to a system. The system is the sound.
To your point, if it's not needed, then that's great. I don't use the ZROCK with my vinyl setup, but it makes a nice difference on my digital setup. I have 3 amps I rotate in with the DW's, and the benefits of the ZROCK varies with each, so I have to adjust its settings accordingly, so obviously YMMV also. The ZROCK is definitely a "salt to taste" kind of product. That said, I will never go back to a subwoofer after using it.
And on my bedroom rig, I just go CD player -> APPJ amp -> Zu DefHeads. Simplicity!
Cheers!