That’s not how the article describes it, at least:

Essentially it creates a vapour chamber-like effect by using heat emitted from the CPU to evaporate a refrigerant, which then moves up a vapour tube into a fan-cooled condenser, where it cools off, condenses back to a liquid state, and makes its way back to the CPU to be heated again—no pump required.

Which sounds exactly like a heat pipe.

Edit: I guess the difference is that heat pipes use wicks and capillary action to return the liquid phase, where the thermosiphon instead uses gravity, which makes it a little easier to produce and higher capacity, but vulnerable to changes in orientation.