Mod.io is not their modding tools. You are conflating the two. The modding tools will allow you to create the mods, mod.io is for packaging, sharing, and loading mods. The only references to actually making scripting changes on the pages are talking about the Script Extender, which is an open source community made tool and NOT part of their mod tools.

There is nowhere on that page that “specifically says you’ll be able to create script mods with their modding tools”. If anything it says the opposite.