I know, and I've subscribed to them early on, but my feed is flooded with other communities and I don't recall ever seing amything from /m/Apple...
I also just went there and the newest posts are mostly days apart from each other...
So "one of the biggest" might be true for the subscriber count, but threadwise not so much activity there.
Which is a bummer, honestly... I'm not a huge fan, but I'd still love to be up-to-date on their stuff.