The WTS is against the transfusion of blood. Storing blood for the purpose of transfusing it into a person is what they object to (even if it is your own blood). Blood that is drawn for testing is, presumably, discarded in accordance with local laws and regulations. It is understood that this blood is not collected for transfusions.
I'm not defending their stance regarding blood transfusions, just pointing out that they have a rational reason for not linking a blood draw to them.