Indeed, otherwise heat pipes would not be so fashionable, these days. It is simply because they work. And if we have a look at air coolers and their reviews, the cooling capacity is not very strongly related to the surface area. It was even remarked that modern heat sinks place the fins too close together, and that air had difficulty going between them. That heat sinks with the fins wider apart, and as such less total area, were more effective coolers.
And it is quite easy to get dust out of a finned cooler. But getting dust out of a copper sponge is different matter altogether.