I wonder if they are describing the Dive Brake arms when they say Cast Aluminum? The main body of the dive brakes between the arms look to be sheet metal. But the arms very well may be cast aluminum. Just a thought.
For sure, the top photo is David Leininger's photo and I'm not sure on the 2nd one. They are the two airworthy A-36A Mustangs: the top one is the Collings Foundation's "Baby Carmen," and the bottom one, is the Comanche Fighters' aircraft - it's unnamed, AFAIK.
This is, of course, "Margie H" static display only - at the National Museum of the U S Air Force.
The Dive Brakes on "Margie H" are not - NOT - authentic, by the way...well, not 100% authentic anyway - there are 14 open slots on the dive brakes (top and bottom) on A-36As, and this one has 15. The "arms" may be originals but not the dive brakes themselves.
Trivia: the lower dive brakes on A-36As (as built by NAA) were about 12% LARGER in area than the top ones.