Thank you for that.
Will, in his testing specifications, does state that the valves were 100% open (except the Monatauk, where noted).
Will, in his article, mentions that the regulator valved stoves did better in cold-calm testing conditions than conventional valved stoves. His results bear that out: The Reactor, Sol Ti, and Sol Al didn't have a great jump in boil time from the warm-calm test to the cold-calm test where as all the conventionally valved integrated canister stoves did. The Eta Solo, JB Flash, JB Zip, and JB PCS all had quite an increase in boil times in cold-calm conditions over warm-calm conditions.
So, the explanation of the performance difference might lie in the size of the jet? I wonder if anyone has the means to confirm this? (I don't have an instrument to measure jet size).
I don't see any physics/chemistry reason why the regulator valved stoves are performing better in cold-calm conditions than the conventional valved stoves, but it'd still be nice to have confirmation that the difference is due to the jet sizes not the valve type.