I am not sure I understand the chart about blood for blood which shows that holding on to it for a cooldown is always a DPS loss. Is there an unstated assumption behind those numbers? Like maybe the idea is that the battle is going to end when you're under blood for blood so holding onto it for a GCD means that you are going to lose a GCD of it later on?

It seems to me that in many fights it would be possible to hold on to it for several GCDs while still getting the same amount of full b4b uses. If the chart is still accurate when you know you are not going to lose any b4b duration I would very much appreciate an explanation about why.

Thanks.