Is Dark | Anti-Jacob the Smoke Monster

It's a popular theory, and one I first assumed. But remember these two scenes:

1. Ben travels underground to be judged (by the Smoke Monster, right?). He is confronted by Alex who explicitly tells him not to hurt Locke (who was really Dark) and follow his orders.
2. Dark / Locke is walking with Ben towards Jacob. Ben tells Locke that his daughter Alex told him to obey Locke and not hurt him. Locke is surprised!

Questions:
a) If Dark was the smoke monster, why is he surprised to hear Ben say what Alex told him?

The two scenes still make sense if Dark / Locke was not really surprised. He illicits Ben's conversation with Alex to remind him of it, and further bolster Ben's willingness to kill Jacob.

I like that theory.