User blog comment:ImaFanMan/How Stand Arrows Work/@comment-30439574-20180705210412/@comment-34882417-20180723145700

Pretty sure SP:TW isn't even an evolution. In fact, I don't think SP:TW is even what the Stand is called. In Part 6, Star Platinum has two stat pages with two different drawings and slightly different stats. One is called Star Platinum, having the ordinary SP stats with an A in Durability and whatnot, and the other is Star Platinum: The World, which has a D in Durability. Because of this, I assume SP:TW is just the name of its ability, like White Album: Gently Weeps or Sheer Heart Attack, rather than an actual upgrade.

Additionally, Star Platinum had no real Stand ability prior to Jotaro's fight with DIO, so I just assume Star Platinum: The World is a sub-stand that Jotaro had from the very beginning but just didn't know how to use until he learned by watching DIO do it.