@altenbach, your comment that many new devices are optimized for low standby power rings a bell. Back when Sense began that was not the case. Perhaps it is time for them to adjust how they report. I know this might be a big deal for them as they have been rounding things to the nearest watt for a long time, but they are good at innovating. I would like to see more precision displayed for small values. In math class they taught us about significant figures. If Sense were to set the number of significant figures to two, then a measurement of 12W would not have a decimal, but a measurement of 9.8W would.
Kasa plug measurements are very precise, per this research by kevin1
When I got my first Kasa HS300, I hooked the whole thing up to a Kill-A-Watt out of curiosity. I found good correlation between measurements, except that as you note the Kasa plug itself consumes some power. If all six plugs were ON with nothing plugged in, the Kill-A-Watt measured 3.6W. If all were OFF, it measured 0W. Turning them on one by one increased the measurement by 0.6W each.