Agreed!
My assumption (and reason for implying) was definitely that using a dedicated KM pause (until) action here, with the 'Reduce CPU Usage' Enabled, would be less demanding than a 'frequent' loop ran once per second.
But I guess a loop and re-evaluation every second, in this context, is not really at all frequent, (even when running 10 of them on top of each other). Also I guess there is in actuality some form of loop running there under the hood of the Pause Until, and my prior testing have indicated that it (over the corse of a few seconds) re-evaluates its condition(s) much more frequently than every second.
So as it takes some seconds for the Reduce CPU Usage to really kick in, it really does make sense that the actual Pause every second is the gentler approach here. (Although, as you say, neither of these puts any modern mac under any significant load.)