That was always a talking point, because there are always going to be cases where a transfusion goes wrong. If you only ever hear about transfusions that go badly, then you get the impression that it's a widespread problem. And if that impression aligns with your view that god wants you to abstain from blood, then it confirms that you are right.
It is the same as those JWs who refused transfusions and survived. They consider themselves an example of why transfusions are unnecessary. They do not consider the extraordinary effort and extra resources that may have been used to provide lifesaving care in lieu of a blood transfusion. They use whatever confirms their beliefs and conveniently ignore the rest.