The technique has a name in the research: battery-based load hiding. Studies consistently find that a battery hides appliance signatures well (the meter loses track of your kettle) but not whether anyone is home. It can't flatten the mean and variance of your demand, and that is what a simple occupancy detector keys on. Two weeks at lower total consumption still reads as "away", because cooking, laundry, hot water and EV charging all drop to zero and the battery does nothing about that.

Also worth knowing: a battery run for price arbitrage leaks more than one run to mask load. Different objectives. Real privacy means trading away some arbitrage margin for a noisier grid profile.

And the data did not disappear, it moved. Your controller now logs minute-level consumption, and for most brands that is a cloud service. The exposure shifted from the grid operator to the battery vendor.