They aren't targeting all 30 million java owners. They are targetting the ones who are most likely to make microtransaction purchases, ie the people who are playing on heavily populated multiplayer servers (single players don't use chat so it wouldn't matter, etc). And from what I've seen, the report function is pretty easy to manipulate, so if you can't renew your account (granted, right now you can, but with microsoft, you never know), a large portion of that player base might wind up off java quickly.

Find the whales, force the whales to move to walled garden.

Granted that's still a dumb idea, because those people want to be playing Hypixel, which isn't on bedrock. So maybe this is just microsoft's move to say "See, no one is playing Java as much" so they can just stop doing java dev.