I have something similar - a 400A main service with one 200A subpanel tied via bus bars to the main and a second 200A subpanel 40 feet away in the garage. Sense has found devices on both (most of my 240V devices are on the nearby subpanel). Detected devices on the garage sub panel include garbage disposals, microwave ovens, oven, dishwasher and dryer heating elements, in sink hot water tap, central vacuum unit).
I don’t think the subpanel division will prevent detection unless current flow to that subpanel is not being monitored by Sense. The bigger issue is likely to be the nature of the devices themselves. I did a list of detectable and unlikely to be detected devices based on my experiences: