The same apply to all other strategic spells I tried (tidal wave, Vertar's howl) so I think it is universal.

If you have enough shards, spells damage multipliers to ramp the damage beyond what can a figurine in unit take and remove entire army stack with that spell a ghost unit of 0/xx hitpoints remain. It's certainly seen on cloth map.

Also in such case tornado does not scatter remaining units. The remaining champion always stays in the place he was once his army gets destroyed. per description he should move randomly.