So, the more I think about "Across The Sea", the more I think that none of the characters truly understands what is going on.
The Losties barely have an idea that Jacob and MiB are superhuman entities, but Jacob only cryptically gives guidance to Hurley and MiB is outright lying, telling each individual whatever they want to hear.
The Others were under the leadership of Ben, who never even spoke to Jacob. They didn't understand anything beyond "protect the Island" and interpreted that from their own corrupt perspective. (Steal babies; terrorize and murder the ones who don't matter -- no problem, "We're the Good People.")
Richard never even knew Jacob was looking for candidates for his replacement. He just blindly followed his boss' orders, believing it was all for the greater good. But he spent years believing John Locke was special and wound up being duped into playing a pivotal role in his own boss' murder.
Now we see Jacob was just another man who got roped into being the Island's protector, but "the Island is a cork holding evil in its place" seems to be his own personal spin on the supernatural events he's witnessed. We certainly didn't see any "proof" in "Across The Sea" that's actually what's going on.
MiB now seems like a man who was turned into a Smoke Monster because his brother threw him into the Cave of Light. Sure, that spat out his original human husk -- "The Devil stole my body" -- and gave him some supernatural powers, but his persona still thinks of himself as a man who just wants to get back to "home" to his people -- even though the Romans of Claudia's time are long gone. If he secretly wants something beyond that, we weren't shown that, either. Does he even know what will really happen if he does kill all the candidates and escape? If so, we haven't been shown it.
At this point, the overall theme of this show is that Man is superstitious and invents magical meaning and purpose for the events he experiences that he doesn't fully understand; but if you pull back, everyone seems to be operating on false assumptions they've invented for themselves.
If Jacob and MiB are all-knowing, that's the opposite of what they just showed us.
If Eloise and Charles are all-knowing, they haven't shown us that, either. And, at this point, it would be in complete opposition to the one consistent theme TPTB seem to be going for.