Now I finished UT before the update, but if I recall correctly, the speed challenges say that if you don't actually have higher init than the challenge, then it will be much higher. Perhaps if you got your init above the suggested number, the difficulty would drop to far more reasonable levels (like a 3-4k shield instead 62k and regular damage instead of one-shotting). If your init is already over the suggested number (which could either be a per ninja init or your teams total init, its unclear if I remember correctly) then I would 100% agree that it's a bug.