If the battery did somehow get discharged, it could have frozen, cracked and leaked. Or it was low on electrolyte and boiled a bit over before a cell went mostly dry, due to the built in battery charger. I've had trouble with batteries going dry, as I live in the northern Nevada desert.
I purchased a 2013 Dodge Charger Police from a Montana state auction, the battery was frozen/cracked and had leaked out all the electrolyte. They'd parked it in September 2018 with a brand new Mopar battery, just didn't keep it charged up. Sold at auction in October 2022 four years later, after putting a new battery in, car runs great. Less than 90k miles.
It was listed as having an electrical issue, car would run rough and was in "battery saver mode", hard to get started, had to use a big jump pack as the small jump pack wouldn't start it (the small one worked fine on other Chargers). Had they swapped in a new battery... they'd have found the old battery was partially shorted. The leaked electrolyte was under the vinyl tire well insert, they may not have noticed it.