They moved Atom into de-facto maintenance mode much earlier than that, when VSCode was much less fauxpen-source than it is now.
A couple points in time:
Pylance, installed by default, won't open source. Microsoft keeps calling VSCode open source. https://github.com/microsoft/pylance-release/issues/4
Same for .NET https://twitter.com/migueldeicaza/status/1537175065380495367