Feather falling boots don't take damage when player takes fall damage

So, I was playing around with redstone, and I made a TNT Minecart trampoline. I put on feather falling IV diamond boots and tried out the trampoline, and I died. Then I picked up the boots, and it hadn't taken any damage, like it normally would. Then I tried it out from a height that wouldn't normally kill you, and it still didn't take any damage.