At the loop there is twice the tensile strength because there is twice the thread count. There is twice the cushioning as well. But the main thing is that there is twice the number of string material to wear/abrade against each other which really is the biggest problem which is of course accelerated by everyone's lack of maintenance. Flemish strings, by virtue of their construction(twist) decelerate the string in a more gentle manner by acting as a shock absorber. The ripping and rubbing of the strands against each other is not nearly as violent.