There isn’t device detection going on with Always On.
You can see the below link for an explanation of how Always on is calculated. There are a pile more articles around if you search for Always On.
Your water heater or fridge which has electronics that use a couple watts all the time, that power is captured in Always On.
Then it is possible for the fridge or water heater to have a signature that Sense detects and calls “Fridge”, but that always on power is not part of Fridge. Its the power above it, since the control boards never turn off.
So to your question of
Does always on include energy from detected (naturally or not) devices or only from the other spectrum?
Simple answer - No, and only kind of. Always on is not detected devices, nor is it other power.
More complicated answer - for naturally detected devices - No. As mentioned above, a device that has always on components (control board for AC, or the lights on the control panel of the fridge) will not be detected as part of the Fridge because the baseline doesn’t change with the transients that Sense is looking for to detect a device.
For smart plug detected devices - The answer is maybe? It seems to depend on the screen, day or moon phase. As @kevin1 said, it used to be really clear. The always on bubble and number was both system detected and smart plug detected always on and you could tell which was which. Then for a while it split out. The always on bubble was just non smart plug always on, but then viewing the AO stats gave you a break down of the natural AO and the smart plug AO numbers. Now, honestly, i’m not sure what it is showing.
But I say its also not Other because Other is power that isn’t identified elsewhere. Always on is “identified” power, it just isn’t identified as belonging to any specific device (when Smart plugs aren’t involved).
What you may notice - if your house ever gets really quiet, your other bubble may go away completely. This is because the power consumption is at or lower than your always on bubble. Sense is doing some basic math in the background as to when to show the Other bubble which seems loosely related to
If consumption is < Always on, only display always on.
If consumption is > Always on, but no detected devices are running, Display Other Bubble with value [Total Consumption - Always On Value = Other Value]
If a detected device is on, adjust the formula above to include subtracting the known device.
It is also possible for the Always On bubble to be more than your whole home consumption. Always on is just a calculation, not a live “real” number. So if you had a 100w ceiling fan on for several days, it would have started out in Other on day 1, but eventually it slides into Always On if its been on long enough. On day 4 of the fan running, you turn the fan off. For a short time after you turn it off, the Always On number would still show the extra 100w until the AO algorithms recalculated.
So yes, AO power at some point was “Other” power, but once its moved to Always On, it is no longer part of other unless it is a device that has just been running long enough to be moved into AO, but has been recently turned off and back to a shorter term power cycle.