I’ve noticed that there are two types of wheel/tire sets used on the A350 (examples shown for -900 aircraft). Is this just a production upgrade for the more common type that has the brake cooling assembly on the outside of the hub? I’ve also noticed the “earlier” tires have four grooves instead of six.
My guess is that the top picture includes the cooling fans and the lower one doesn’t. Several Airbii have cooling fans as a customer option for operators in warmer places with tight turns. If you’re almost always doing 90-minute turns on long runways where you can use T/R and spoilers to slow, most brakes can cool sufficiently before you launch again.