I hope that this is just a rebranded system showing the redyness of System76 and raising awareness about such products so that they're better positioned for the ThunderX2 release later this year.
ARM the company does design both low power and power efficient implementations of the ARM architecture. In fact for some specific power targets (mobile for example) they are more efficient than the corresponding Intel CPUs.
This is still irrelevant as Cavium design its own ARM cores from scratch (i.e. it doesn't use ARM reference designs) specifically for server use; now, they are not very good, but that's another story.
I agree, but only if the measurement of power efficiency includes idle periods -- eg. "browse for 5 minutes, lock phone and wait 30 minutes, repeat".
I don't believe you can provide a source showing an ARM CPU executing a particular workload (i.e. not including idle periods) at greater power efficiency than a same-generation Intel x86 CPU.