To understand antidive look at the upper control arm. The pivot is angled upward toward the front. Someone recent said their MII front was installed backwards and the upper control arm sloped downward (really bad). Anyway, when braking there is a horizontal force acting in the forward direction on the upper ball joint and the upper control arm geometry turns this force into a downward force at the ball joint. The downward or antidive force is proportional to the braking force. Pretty cool. But how effective is this? I don't think McPherson struts have the same effect but most cars nowdays use that type front suspension.
Easier explanation: brake dive is when the front brakes are applied the resistance on the wheel rotation makes the front end want to tuck under,
similar to what happens when you apply only the front brake on a motorcycle. Anti-dive is geometry built in that resists that force.