I don't mean to say that they are doing anything illegal or unethical. It just looks cheap to post a screenshot that looks like pixel-perfect copy of VS Code. Don't these people have a vision?
I think what they want to focus on is not the editor itself but rather everything around it and where it's run. In typical startups, you try to focus on your core product, so reusing the editor from another project makes sense, as they don't mind the details about the editor itself.