Sky splitting is ACOC, it’s been present for years now. It’s the furthest thing from an asspull here.
that’s not what a retcon is. What happened to Sanji was character development, where his dormant genes were reawakened by a mcguffin. Was it sudden? Sure. But we already had a plot point via the Sanji flashback about Sanji’s DNA and the raid suit was long established. None of this was an asspull or retcon.
Nothing Robin did is extreme though? She made a bigger body and had an aesthetic change. She’s been creating body parts out of her Devil fruit limbs since Dressrosa minimum and has been growing her limbs to extreme sizes since Sabaody. She also learned from two characters that were established over 200 chapters ago and we know she spent time with.
Sky Splitting BECAME ACoC at 1010 once Oda introduced that. It was only foreshadowed really at Roger vs Whitebeard because their sword weren't touching.
Again, Shanks vs WB are touching sword. Kaido vs Big Mom too.
Since when character development is killing all you had build up for that character? It was retcon since her mother sacrifice for him to not have that DNA bullshit. Is also retcon since WCI Sanji managed to beat up Yonji and even made his face like that but Sanji's is immune to swords and bullets because of the same DNA/Exoskeleton. And DNA being awakened because of RS is just... bad writting.
Robin during all One Piece was using her DF and making herself a image similar to an Angel not a Demon. This is retcon. Not said anything about her Fishmen Karate that she learned with Koala/Coby.