In general, the answer to this is "yes this is possible, it depends on how the CTs that measure power flow are setup. An example of this is, I have "whole home backup" with the exception of my Tesla Wall connectors (I know this means its not actually my whole home, but... lol).
Anyway, as I mentioned my tesla wall connectors are the only device not backed up. In my case, they were left in my original panel, and every other load in my home was moved to the "backup loads panel". My gateway still sees my wall connectors, and if I charge my car, it will (very quickly) drain my powerwalls to whatever I have the reserve set to.
if I am off grid, however, the wall connectors dont work (since they are not backed up).
This is what you are asking for, which is the ability for the gateway to see non backed up loads. Whether its possible or not depends on where the panels are, and whether a CT that monitors power flow can be placed in such a way that the gateway can see those loads.
I didnt even know to ask for this, and my home was setup like this for me (I had really good Tesla installers). I have read others here either dont have this, or have had to specifically call it out, and it depends on equipment placement, etc is what I remember reading here.