I do similar in plastic bottles from the cheap crap apple juice in supermarkets. Better results than from nice apple juice. No, I don't know why. But it's fun. I've not tried a longer secondary fermentation, I will next time.I have spent about a decade working on home brew to get close to that Normandy style. FWIW I have found if you ferment until dry, then bottle for a secondary fermentation with about 7g sugar per litre and leave it for a few months in the bottle, you can get close enough for Devon ... no messing about with chemicals, just fresh pressed apple juice and a little cider yeast to make it more reliable to start.