Sort of a). WSJ and NYT (and others) decide and control whether to allow entry to a walled article via google. This isn't a hack or a workaround, it's what WSJ and NYT want to happen (or they'd disallow it). You're not "cheating" when you enter via google, you're going in via a side door labeled "Welcome."

And sort of b). It's just a decision to use "the link that works for everyone" (with NYT/WSJ blessing), instead of the direct link that only works for subscribers.