Riot isnt a trigger, but alters the creature as it hits the battlefield, so Pelt Collector tracks right if you choose big over haste
The problem with this was that players could, for example, trigger a Werewolf by playing no spells that turn and then, when the trigger was on the stack, play instants
Its an incredibly elegant and carefully designed solution to the onboarding problem that a lot of TCGs have, and I wouldnt be surprised if other card games look to this for their own equivalent in future
We've certainly noticed a surge of interest in Warhammer 40k around the release of the game, so it's not inconceivable that that's translated to more players building around one of its characters
Check out the transforming Gwen Stacy/Ghost-Spider card
Crystalline Sliver outright nullifies all targeted removal along with a number of other solutions