What the article suggests is that ceramic is good for the pressure, but not for tension. It shatters. I presume that the carbon fiber threads help that from happening, because they hold it together.
A vest that shatters would be dangerous if there is more than one bullet. The first would shatter it, and those that follow would then go right through.
Carbon fibers are known for their high tensile strength for the weight involved.
It would be lighter for the most part and as an Ex Grunt that is good.