P-38 doesn't have dive brakes...
ack-ack
But the P-38 dive recovery flap is actuated by the dive brake key assignment in Aces High so the confusion is completely understandable.
And the design of the real thing is identical to control surfaces that are today referred to as speed brakes, spoilers or dive brakes. The aircraft I currently fly has 8 panels that look just like a P-38 dive flap with the exception they are on the upper surface of the wing and their primary function is to kill lift, hence they are called "spoilers". We use them as dive brakes but they aren't called dive brakes.
The speed brake (or dive brake if you like) on the F4 Phantom is remarkably similar to the P-38 "dive recovery flap".
So calling the P-38 "dive recovery flap" a speed or dive brake is not all that unreasonable. It was designed to assist in recovery from exceeding critical mach but it functions as a speed brake as well and I would imagine it was used regularly as a speed brake by P-38 pilots.