IMO, it is too bad so many batteries are sealed now days
In the past it was fairly common to be able to test individual cells and see right away you had a problem
A Hydrometer test to check each cell, We also used a Sun Machine battery test station to check dead shorted cells, this took all of the guess work out of the equation
Yep guess you could circumvent the seal but since those days I can't help but think our water is cleaner now.
Seems these days every year there are inland floods and hurricanes trashing many vehicles that their fluids enter the water system. I had a 4 tooth bridge that was gold cast with porcelain face about 1965 that when I got around the stations charger when its on had me tasting metal. Happened every time I tended one being charged.