You have this backwards.

When you reduce draw weight, your BRACE HEIGHT gets longer, but your ATA generally shrinks. Decreasing draw weight is decreasing the preload 'levering action' on the limbs, which lets them relax slightly compared to max draw. That means your tips move together slightly, lowering ATA, and lean further away from the riser, increasing brace height. You'll also see a slight increase then in draw length when you drop poundage.