No that's not right.
If you were calling a function which might return null (String | Null), you will already have null handling at the call site, but if you now change that function such that it never returns null (String), you still have the (now unnecessary) null handling, but this doesn't hurt and you don't have to change anything at the call site.
Likewise, if you were passing a String to a function that doesn't accept null (String), the call site already made sure that the parameter isn't null, and if you change the function so that it does now accept null (String | Null), again nothing needs to be changed at the call site.
I agree that this can be nice when done right (Clojure), but null is a high price to pay for this convenience.
I must admit I’ve never had this problem in application development. In fact, I do want to change my callers because strengthening the contract is an opportunity to simplify the callsites - they no longer have to handle the optionality. The change might carry some semantic meaning too, why are you getting x instead of Maybe x all of the sudden? Are there some other things you should reconsider in the callers? I can see how it could be useful in library development, but there are also patterns to account for this that are idiomatic to Haskell.
> I agree that this can be nice when done right (Clojure),
I don't think Clojure has untagged union types like TypeScript or Scala.
> but null is a high price to pay for this convenience.
Why would it be? Untagged unions prevent null pointer errors just as much as option types do, only they don't have the discussed disadvantages of option types.
> Why would it be?
That's literally what they explain in the rest of the comment.
No, they don't reference any "high price to pay", only that they personally didn't need the advantages of untagged union types so far, and that Haskell (allegedly) has patterns that would play a similar role for libraries.