There was another really bad consequence of the societies changing their mind on something.
For years JW hemophilics were told by the society that they could have one dose of a blood fraction but no more as that would constitute a 'feeding' of blood which they felt was wrong.
They had told this to witnesses who had contacted them. After a while they changed their mind and decided it was ok to have what was necessary for them. So they contaced ones whoi had written in but of course could not tell the ones who had phoned in.
So it may well have happened that many JWs died simply because the society had given them wrong imfo.
Apparantly it was put into print 3 years later but not in a very clear way, and certainly not saying that they had any new light on this.
Info on this can be found in Ray Franz book 'Crisis of conscience'