As I understand it, the issues are with the purifing processes donated blood goes through before being available for use in transfusion.
Also the person would be be excluded from the faith if they accept blood transfusion.
Think it was in 2000 it was decreed that a witness would no longer excluded from the faith.
There is a device called the cell saver that processes the patients own blood at the bedside. I think I’m right in saying JW will accept this BUT the cell saver is used more in planned surgery requires specially trained staff to operate it so is not alot of good in an emergency situation.
There are many complicated issues that might seem bizarre to non JW people but their beliefs have to be respected however foolish we might think they are.