Question about Tornado/Gathering Storm build

Hey all,

I'm trying to follow this guide here: https://maxroll.gg/last-epoch/build-guides/tornado-shaman-guide

The guide says "Do not put Gathering Storm on your Action Bar... ...Gathering Storm is cast from Tornado".

For the life of me, I can't see where gathering storm is getting proc'd when casting Tornado. At first I thought maybe it was a typo and they meant "Storm Bolts", but they've spec'd points into Gathering Storm nodes that rely on Storm Stacks, which only accumulate when gathering storm is used.

What am I missing?

Thanks