To be fair, at the start of the gen Treads was better in a lot of match ups (always outspeeding scarf chi-yu with booster or a spin was super good to keep the fish in check) but with some bans and some additions to the tier those match ups became bad for Treads.
No offense but that's one scenario and that's not even a good enough reason to prefer Treads over Tusk, because you still couldn't switch-in into Chi-Yu, booster is also one time use and it's usually preferred on mons that are able to sweep or at least knock 1-2 mons. Treads is too weak in order to have that happen (able to sweep). I understand that Treads had / still has it's own niche but viability wise it's not close to the various things that many tusks sets can do.