They're definitely not correct for .NET - you forget WinRT. That ecosystem was much more heavily invested in native interop from the get go - COM interop, P/Invoke, various runtime features like unmanaged pointers and unions etc. So once native async became a thing, .NET developers expect to be able to interop with it, as well.
> Runtimes that choose to roll their own green threads, like Go, and I guess now also Java, are effectively stating that their convenience is worth the inability to interface well with async code outside of their runtime.
You'd still be able to interop with async code outside of runtime, you can still model the API as callbacks for the interop purposes where needed.
But yes, interop has sam trade-offs. Which are, IMO, entirely correct trade-offs to make for Go, Java and .NET (and overwhelmingly so). But they are probably not for (as an example) Rust, according to it's goals.