You might like to read our article about pressure regulators. It was published some time ago.
Basically, that pressure regulator IS a needle valve, with some extra springs etc. All the magic properties ascribed to it are total BS, made up by the spin doctors to get you to hand over your wallet. Some of the claims are absurd; the rest are either stupid, irrelevant, or false.
I will add that the worst claims seem to have come from the distributors, not the SOTO company.
As far as efficiency goes - that is a function of the pot diameter and the user. Turn the stove up full bore and you get low efficiency. Old news.
Roger Caffin (PhD, physics)