I’ll give it a go …
Here’s the FAQ answer as to why in a Naim system the signal is routed through the Power Supply:
https://community.naimaudio.com/t/why-naim-route-the-pre-amp-signal-through-the-power-supply/73
The reason is that the absolute earth reference for the system is the reference for the pre-amp, which is the SUPER-CAP, HI-CAP or FLAT-CAP earth. The signal is routed from the pre-amp to the power supply using the same interconnect that takes the power feed from the power supply to the pre-amp. It also connects the two earths together. This minimises differential voltages caused by interfering electric or magnetic fields being generated between the power feed, signal and earth, so maintaining the correct relationship between signal and earth inside the power supply. The power amp is connected to the properly referenced signal at the power supply output.
With two Hicaps, the 2nd Hicap isn’t directly connected to the common ground point (for the pre-amp, hicap 1 and the power amp) that exists inside Hicap 1. Instead, the connection is there, but via Snaic connection to the 282 and then the Snaic connection to Hicap 1. The resistances and additional cabling involved in this indirect connection means the minimising of differential voltages (described above) related specifically to Hicap 2 is less effective.
Note, this doesn’t mean there is a ground loop when using two Hicaps, it just means the star earthing benefits are reduced for Hicap 2