Well, I think ultimately the bloodless route is ideal. However there are certain situation where it becomes necessary. Much like chemo is not ideal for the body but in certain situations it becomes necessary.
I think they see that a total blood ban was an error however to many children have been sacrificed on the policy a quick 180 would be unacceptable. But know thanks to medicine blood has been broken down for different situations.
The watchtowers hope most is that down the road all these things can be treated by the so called fractions that they will allow. This will allow them to undo the policy without actually undoing it.