I'm very suprised about this, I can see it if the charger was a dumb old fast charger, but I would not have expected a CTEC to cause any damage, I doubt it could supply much of a maximum current in any event, although it does seem to be to much of a coincidence.
I have a CTEC charger on my motorhome, linked to a solar panel, the car and domestic battery , so it's entirely possible that the car battery could be receiving a charge when I start the engine, and that would surely be part of the design of the thing.