F# Spec doesn't mention private representation Discriminated unions

For example, in this type:

```
type HtmlAttribute =
private | HtmlAttribute of name:string * value:string
```

What's the effect that `private` should have? I see that in C# projects, I no longer have the `NewHtmlAttribute` constructor, but I can keep doing pattern matching and create new values with `HtmlAttribute("a", "b")` in F#. Is that the intended behaviour? I was expecting to not be able to create new values using the union case constructor, and force people to use a static method that normalizes the arguments