I personally find those "helpful" things to be truly, well, helpful. For example the input validation, anti-forgery token validation, simple cache control, etc.

Again, not saying you can't do these things in node. The two technologies can easily accomplish the same goal. But if your primary concern is avoiding JS, why would you choose a technology that is built entirely upon it?

Node.cs might make more sense, I agree. I have a feeling the existing ecosystem might bring its own problems with the author's approach, because your C# code may have trouble integrating with those existing libraries, if the underlying generated code does not behave as the Javascript library expects.