I've just been reading the watchtower's blood policy and I think I've got it. I'm not sure but this is what it may come down to:
The WTBTSs give you a "one shot" deal.
If you accept a blood transfusion once and express sorrow and regret, you're forgiven and can remain in good standing. After all, how many blood transfusions do you think an individual will have in a lifetime?
Actually, I have to applaud good PR. This is their PR working at its best. You can have your whole blood transfusion, remain in the organization and the WTBTS can still claim that blood is not allowed.
Of course, the whole concept is written so ambiguously that it is hard to grasp that a whole blood transfusion is good for one time only, without incurring consequences.
Of course, because they still profess that no blood transfusions are allowed those sincere minded members will still forego their lives and the lives of their family members in their attempt to "buy" everlasting life. These are the folks who will only hear "no blood" and will not take advantage of their "one shot" deal.