That's vscodium

It's exactly the same as Google Chrome vs chromium. One is very much not the other

I think it is a poor analogy.

VS Code and Visual Studio IDE are fundamentally different products. One is a lightweight editor, the other is a full IDE with different architecture and capabilities. Chrome and Chromium are the same product type (browsers) where Chrome is built from Chromium source with proprietary additions[1].

A better analogy would be VS Code vs VSCodium, which actually mirrors Chrome vs Chromium: same codebase, one with Microsoft's proprietary bits removed, or Fedora vs RHEL.

[1] Both Google Chrome and Chromium are maintained by Google.

I think that's what he was saying. But VSCode is open source though, which he's wrong about. CHrome is not open source.

Google Chrome is not open source indeed, but Chromium is, which is what Google Chrome comes from.

Microsoft plugins aren't open source.