Putting on my research-mode EE hat, I’d think that the IDEAL Sense configuration would be to have a set of current sensors (the ‘collar’ device, but smaller than the ones monitoring the main feed) for each single-ended branch circuit.
My assumption is that the information from the main feed will typically be able to identify the devices on the two-phase circuits (ganged breakers) because they are usually feeding a single device (e.g. HVAC, Electric Oven, Electric Dryer, …).
Monitoring the current on the other circuits, though, ought to allow quicker & more accurate identification of ‘similar’ devices, such as ceiling lights on one branch vs ceiling lights on another branch, or the use of a hair dryer in one bathroom/bedroom vs. another bathroom/bedroom (when they’re on different circuits).
That is a rather significant technical challenge, I know, to provide both cost-effective sets of sensor leads (probably cabled in groups for ease of installation and connection), the size of the sensors (so they’d fit in the electrical box), as well as the connection ports to the Sense device itself.
Maybe that’s the “second generation” version of sense. If it could be done for, say, only a 50% increase in price – I’d choose it!
Even if there is only the capacity to monitor, say 16 of 24 branch circuits, by careful choice of which branch circuits are monitored, I’d think the device detection could be much more accurate and faster. (e.g.: I might not chose the circuit for the garage, for example, because the primary items on that branch may be the opener and one exterior light.)