I thought that was supposed to be fixed by contenteditable plaintext-only. Why was field sizing still necessary?

`contenteditable` is an HTML attribute but it depends on JavaScript to do anything useful. This problem is one of layout, CSS's domain, so `field-sizing` solves it while leaving HTML form elements to do the actual job of taking input.

At least recreate their demo for us to showcase the fix. But I feel like it would be a let down that answers your question.