It's not that it was disturbing, though the wording fit at the time, it was that it shown a brief Pluto scene where Astro looks like he's gonna get killed and then cut quickly to him flying in the air. It just symbolized his death and ascension or maybe I'm reading too much into it?
Looking back at it , I wish that the renaimated segment was apart of a promo for an anime remake of Astro Boy because those few seconds were better than the 2003 series we got.