Yeah I said the same thing, if it was a toggle of some sort. Honestly they could fix it easily by making the ability also read: "Also causes colossus smash to increase damage taken from Fire damage caused by you by ~32%"
Or some such. I am betting we see some kind of synergy or buff. Right now the only bonus comes from the auto attack damage and its pretty minor.
Anyways, this thread is really long with now (mostly) useless information; I edited my post with new information and moved it over to the new thread to continue discussion there.