Maybe the way how editor interprets beam models doesn't connect model scale to beam's size as it does to the particles or the closest beam's relative - ribbons. I'd call it a bug, becasue why would something that works for everything else not work for something one. So, most probably, the only way to scale beams is to create a model with multiple animations, each of which would have different width of the beam. So, actor would switch between those instead of changing scale.
Maybe the way how editor interprets beam models doesn't connect model scale to beam's size as it does to the particles or the closest beam's relative - ribbons. I'd call it a bug, becasue why would something that works for everything else not work for something one. So, most probably, the only way to scale beams is to create a model with multiple animations, each of which would have different width of the beam. So, actor would switch between those instead of changing scale.
open the beams that do and do not scale in cse, and check what bones do they have
maybe there's an obvious difference, that will give me the idea of how to make a scalable beam model wise