The ".NET Spec" doesn't have the name ".NET" in it anywhere - .NET has always been the name of Microsoft's implementation of the Common Language Infrastructure spec (https://www.ecma-international.org/publications/standards/Ec...).

Now that Microsoft itself (and Mono + Xamarin) has multiple implementations of the CLI, it's spec'd the API surface area that is to be expected across the multiple implementations (since this is explicitly not covered in detail in ECMA335) - hence the name, .NET Standard.