Hi BobM,
Not to confuse on things, but here's how I understood it.
Piccolo - load before amplification of the current, no transformed impedance, current device because of the transistors.
SUT - amplification before loading of the voltage, transforms the impedance it sees, obviously works on the voltage as seen from the primary reflected to the secondary (with voltage gain).
BTW, I am in the SUT camp. I much prefer it than the Piccolo in my system, but I use the Piccolo now and then.