Yo!
HP ice in theory might sound nice on Tornadus but in reality it doesnt hit anything which Hurricane doesn't. The calcs youve shown arent particularly special when you realise both Chomp and Lando are 2hkoed by Hurricane regardless, not to mention youre sacrificing either Superpower or Heat Wave, meaning you are now effectively walled by Ferrothorn, Heatran, TTar, Skarm, etc. You also sacrifice U-turn, the biggest reason for Tornadus's success, meaning you now lose switch initiative. Basically, you are sacrificing all of the benefits associated with using Tornadus to perform a role which can be much better done by something else.
I think this excerpt of text from an old thread might help you. It outlines the difference between an effective set and a gimmick, which is what many players seem to have trouble identifying. (the quote is written by Halycon)
Hope this helped.
HP Ice gives Torn-T ability to check Garchomp/Landorus-T/Gliscor,by switching into EQ and hit back."it doesnt hit anything which Hurricane doesn't" is true,but it can OHKO something Hurricane can not.
252 SpA Life Orb Tornadus-T Hidden Power Ice vs. 252 HP / 8 SpD Landorus-T: 364-432 (95.2 - 113%) -- 68.8% chance to OHKO
252 SpA Life Orb Tornadus-T Hurricane vs. 252 HP / 8 SpD Landorus-T: 247-292 (64.6 - 76.4%) -- guaranteed 2HKO after Leftovers recovery
And can KO Garchomp/Gliscor on a higher health range without the risk of miss.
It is not a meaningless move for it,though team dependant.
An example of Pokemon often run move that "doesn't hit anything its STABs don't" is Mega Diancie,who runs Earth Power at a rate of 63.617%,while HP Fire at a rate of 36.917%.It is easily to find HP Fire is a better coverage move for Mega Diancie - Even after you take the loss of 350 Speed into consideration - Only if on a situation that your opponent has to switch out and you can predict freely.
Heatran can be 2HKO from Diamond Storm (if HP investment exists would be 3HKO),Spec Magnezone can be 2HKO from HP Fire,Bisharp has a chance of 37.5% to be OHKOed by Moonblast,Klekfi runs Magnet Rise,Mega Metagross is both 2HKOed by HP Fire and Earth Power after Stealth Rock,so why people need Earth Power?
I mean,in a metagame where pivoting,predicting and double switching are very common,there is a big chance to face other popular threats 1vs1,while both cannot switch into each other in paper,such as Tornadus-T vs the Ground/Flying-Types,Mega Diancie vs Bisharp,Mega Lopunny vs Landorus-T,and many other situations.The move that "doesnt hit anything which Hurricane/whatever doesn't" may cannot make your checks fewer,but can increase your space to predict or operate,allows you to check/be pivoted into/double switch into/revenge kill(or not be revenged by) something that you cannot without it.