Yeah, they do, but that has to do with the tendency of airflow in evaporator coils to straighten out and become laminar if those fins would be flat...
It does not do much in the violent turbulence of a propwash. I messed around with that in my helicopter days, where those separate headsinks could be oriented any odd way. Did not make any measurable difference.
I also figured out that if you drill holes in the fins, the diameter being equal to the fin thickness,you actually add surface area to the fins, because the bore wall has twice as much area as the fin area drilled away. So I had a blast with the drill press and drilled oh, I don't know, something like 200 holes, adding about 15% of additional surface, but whaddayaknow, it did not do anything, because the air in those holes remains stagnant... Dang that "small scale of things"...

Basically, adding surface does "something, sometimes". increasing effective airflow works LOTS better.
Baffling (bulkhead with a silhouette cut-out) works, poorly! It only forces air through the fins at the location of the baffle. Tunneling works way better, and the closer to the fins, the better, as long as you can make sure the air has no other way than to pass through that tunnel.
What I did with my radial worked remarkably well, improving cooling a huge deal while at the same time reducing drag of the plane, increasing airspeed (and thus cooling air flow), but radials in general are fairly easy to "tunnel" due to the fact that the pushrods are in front of the cylinder. The Boxer is difficult to tunnel because of the placement of the rods and how that affects possibilities to really tunnel it in tight.. .