VS Code is not based on Atom - it's built on Electron, the app framework Atom is also built on, and uses some of the same Node packages Atom developed.
Electron was extracted from Atom and was originally named Atom Shell. I don't see your point.
Electron was also not extracted from Atom - it was always extracted as atom-shell. It was just rebranded as Electron. Atom ≠ atom-shell.
Maybe we aren't speaking the same language. Here's what it says on electron.atom.io: