Earlier quoted context omitted.
VS Codium and other forks don't (maybe can't) use the official VSCode extension market. Because a lot of goodness, like the ability to refactor and debug PHP, is coming from the extensions and the extension ecosystem, it can be a big deal.
However, one can still add that marketplace, if one wants to do so. So people could still have access to the same extensions (which might be a privacy and telemetry or spyware risk), but at least not have the in-built telemetry.
> Found running server...
>
> *
> * Visual Studio Code Server
> *
> * By using the software, you agree to
> * the Visual Studio Code Server License Terms (https://aka.ms/vscode-server-license) and
> * the Microsoft Privacy Statement (https://privacy.microsoft.com/en-US/privacystatement).
> *
>
Many of the interesting extensions (Microsoft's language plugins, the remote extension pack, the .NET debugger) are licensed only for use with Visual Studio Code. Even if you hook into the VSCode marketplace, they could sue. They probably won't unless you're rehosting VSCode externally or something, but the risk is something most companies probably don't want to take when the software is free as in beer anyway for the "real" builds. (And if you're telemetry sensitive... just block the domains? I know, easier said than done, but you can do it.)