Here's what I read: they had a solution written in Node.js; they rewrote the solution in .NET Core; it was 20x faster. It's anecdotal, sure, and Microsoft prompted them to write it, and YMMV, but they did a thing and it had a remarkable result so they've remarked on it. It's not realistic to expect them to take the time to build a representative sample that doesn't expose any of their proprietary business logic; they're running a business and have more important things to do.

Anecdote of my own: I was working on a web bug that had to generate a few v4 UUIDs on every request, and using a version of Node for which the libuuid wrapper wasn't working, so I was using the fastest script-based generator I could find, but it was still too slow. A .NET Core version of the same code handled something like 40x the number of requests on the same hardware.

If nothing else, it demonstrates that using the same solution for all your different problems is A Bad Thing, because there are surely things that .NET Core is not particularly good at either.