No, it's not true. Or rather it's an over-simplifcation.
Really it's not much different to 4E's bloodied condition - there is expected to be some visible effect, obvious impediment or injury to a creature when it is down to 50% or less of its maximum hit point total.
There appear to be no mechanics associated with it, it is just a descriptive element.
Yes, it is true. When you reach 50% hit points, you have suffered "cuts and bruises" and when you drop to 0, you have taken a serious wound and are knocked unconscious. You are then "dying".
Who dies from losing heart? No one.
There is an explicit implication that the first 50% of hp are superficial and the lower 50% are physical and when you reach 0 you are dying (from physical trauma).