How is this different than C#? What new concepts does this bring that C# doesn't?

20 years ago there was some momentum behind Visual Basic .Net; but the language was so similar to C# that it just wasn't worth using. There was a joke that .Net was a "skinnable language."

BTW, there's a whole nitpicky/semantic argument that C# isn't null safe because of the null forgiving operator. That will probably come into play with G# if the null forgiving operator can be used from C# to pass null into G# code that doesn't expect it.