The Watchtower has a long history of not accepting many science concepts. They use to preach that receiving an organ transplant was the same as cannibalism. To me, that isn't much different than their stance on blood transfusions being the same as eating (or digesting) blood.
They let go of their ridiculous stance against organ transplants in 1980, but for some reason, they are having a difficult time seeing the error of their ways with blood transfusions.
The AJWRB website has a great page that showcases the Watchtower's silliest science and medicine claims in their earlier literature. http://ajwrb.org/the-watchtower-on-science-and-medicine