On regression look here:
Identification requires a combination of distinguishability and repeatition (consistency). In practice, bigger relative power peaks will distinguish themselves. In theory though any consistent peaks (or troughs for that matter) in the signal could aid detection.
By way of a seemingly trite example:
My toaster is quite consistently detected by Sense natively. Since it’s initial detection I have yet to figure out what will throw it. A second toaster would no-doubt make life difficult, for Sense and me! That said I haven’t deliberately tried to throw it off and, I suspect most importantly, my home has a relatively simple electrical profile … especially in the morning perhaps before everything wakes up. I have no doubt that Sense could get even that simple device wrong.
My thought experiment example falls back on a house with 2 lights. Both the same; identical bulbs; perfectly wired with identical switching. Nothing else is running. Sense (or a human for that matter) will never be able to distinguish which bulb switches on and off by only looking at the overall electrical signature from the house. Now imagine both bulbs being switched on and off with normal human regularity. The overall Sense graph will give you an accurate picture of the house power consumption (0 bulbs on; 1 bulb on; 2 bulbs on) but no clue as to which rooms/bulbs were lit. On that front it will be perfectly imprecise and there is nothing, given my perfect house, that will clue Sense in to which bulb is on, or off from the electrical signal alone.
Now imagine that the bulbs are switched on and off faster than once every half second. A lot faster. As @kevin1 points out, this is the resolution of the Power Meter view. What is your own expectation of being able to track how many bulbs are on from the Power Meter view in that case?
My point is that comparing Sense’s ability to disaggregate devices to a human’s ability is not (mostly) valid. On a macro level it often looks easy but on a micro level is where it really counts, and where it gets hard. It may seem simple from looking at the Power Meter but more often than not it may well be near-impossible. It’s hard to divorce yourself from additional knowledge: I know my toaster is on because I’m making toast!