This is a common misconception. Electron is a really tiny slice of these two text editors. Atom and VS Code are text editors and they have completely different

This is a common misconception. Electron is a really tiny slice of these two text editors. Atom and VS Code are text editors and they have completely different code bases for the text editing, so there isn't anything that can be moved upstream. Monaco, the text editor at the heart of VS Code, is just a lot better (and older and more mature) than Atom's. Perhaps Atom will eventually catch up or simply switch over to Monaco.