Yes I agree, the solution committed is horrible, but nobody cares any more. We have entered a very strange parallel universe where because AI can work things out it's easier to take solutions that are sub optimal and just churn out (potentially) buggy features.
I care. If you can loosely point me in the direction of a better solution I'll do the extra work.
Interesting I downloaded dataset-agent and removed various different styles from the textarea (with an intention of providing a PR) including the overflow-x: hidden and I tried Safari and Chrome with both the global Mac setting of Always showing horizontal scrollbars on and off. It NEVER shows the scrollbar for me.
Do you have an extension installed that is doing something weird to your textareas? Maybe I'm doing it wrong but I think for now overflow-x is fine if you are experiencing it and I am not! Let's all get on with our lives I was probably a bit overzealous about caring all that much about a perfectly fine CSS fix.