This will allow users to upload KubeJS scripts. KubeJS is a mod very similar to CraftTweaker in that it allows you to change recipes. It also has some added functionality, but that is better documented on its mod page (https://www.curseforge.com/minecraft/mc-mods/kubejs-forge)
I also noted that .zs files (CraftTweaker scripts) are already allowed, so it makes sense to support KubeJS (which is becoming a lot more common in modpacks these days) as well!
(Zipping the script first does work afaik, just not ideal)