The bible says that nothing should be added to the things written, but that doesn't stop them from making up all kinds of rules not in the bible. It's not that fractions are wrong, its that there is nothing wrong with taking blood in the first place. This splitting hairs is just their attempt to get out ofan embarrassing doctrine they won't admit was wrong in the first place.
Also not in the bible:
Judicial committees
A governing body
Field service reports
Telling people how to spend their time
Not watching R rated movies
No eating birthday cake
A specific number of hours in meetings
No higher education
And on and on and on. The Watchtower has made up all these rules when there is nothing in the bible that justifies this kind of micromanaging of people's lives. They make a few things a conscience matter to give the illusion of people having control over their lives, but then give the distinct impression people are really better off just not doing the thing. They have created a whole group of people can't think for themselves.
They are so concerned with obsessing over peoples sex lives and making sure they don't have any free time they have completely lost the meaning of what being a Christian is. If they believe Jesus died for our sins, why are they so obsessed with rules? Jesus said that you will know who are Christ's disciples because they have love among themselves, something that is completely lacking in most congregations. Instead they have a group of people trained to judge each other over every little matter.