I've been sewing for years and never knew this.
Now I know why my needle comes unthreaded after using the cutter - the thread is twisted so tight that when I engage the cutting mechanism, it releases the tension, right back up out of the needle!
I only use cones - so ALL of my thread should be used VERTICAL. (I use the cone spool.) Why, then are do all the machines COME WITH HORIZONTAL SPOOL HOLDERS???? (I've never seen a cross wound small spool of thread!)