I can’t say I’ve ever cooked rice by throwing it into already boiling water though,
Do you mean when replacing the parboil water? At that point, the rice would already have been brought to a boil gradually. Discarding the parboil water and pouring in fresh boiling water wouldn’t be like throwing dry rice into a boiling saucepan.
Or are you thinking of changing your process, by no longer bringing the water to a boil with the rice already in it, but instead waiting to add the rice until after the parboil water has reached a full boil? I realize that’s what the infographic shows, but I don’t think it’s necessary to do it that way. If anything, I would expect your way (bring rice & water to a boil together) to pull out more arsenic.