Nothing becomes part of anything. It’s a sanity check that’s applied to any device that Sense thinks has turned on that exists for a variety of reasons. As a very simple explanation for how this check works:
Any time any device turns on the device model says “I expected this device to be using X watts”, Sense replies that the house is currently using Y watts in total with Z of it being reported by other devices. Provided that X + Z < Y, then Sense will show that device as being on. If X + Z > Y then Sense says “No, this model must be wrong, something else came on instead.”
Again, that’s a super simple explanation. The actual checks that are performed are a good deal more complex than that, but this is the basic principle behind the wattage check. If the Always On is over-reporting then it’s going to block Sense from saying that devices turned on until the total wattage in use is greater than the Always On + anything else that’s also running.
Sense does not put this power into your Always On. The Always On value is not going to change, it is not going to grow, and the power from those devices was not previously being tabulated into the Always On.
In 99% of user cases, the Always On value should never be over reporting. This will only happen if there are devices which are left on for 20+ hours which then get calculated into your Always On value and then you turn those devices off. Until the next period wherein the Always On recalculates the value for Always On will be higher than it should. It’s super rare for this to ever be significantly higher than what the actual Always On value should be.
So, yes, if you forget that you left your basement lights on which use 200 watts and then turn them off a day later, they are going to get converted into Always On value for a time until after you’ve shut them off. During that time period, it’s probably likely for Sense to miss some things like your fridge turning on, but even that is more rare because there’s some fuzzy logic in how Sense allows for over-reporting from devices so if there’s some other light in the house that’s using 120 watts that’s on, then your fridge will probably report fine because Sense won’t care that the total device usage is 80 watts or so off from the overall usage.
Again, that’s simplified. The fuzzy leeway that Sense allows isn’t any set specific value, it depends on a lot of other factors. And none of this even factors in smart plugs which are a completely different thing.
Regardless of all this, the Always On value for a home should be relatively stable and consistent. If you are noticing that your Always On in changing by high values throughout the day or day to day; certainly check with our support team to make sure there isn’t a bug in the app or in the detection of something, but outside of a bug it’s caused much more by how you are using energy. There’s something that’s being left on for far longer than it probably should be, and I’d certainly consider that a vampire load.