The non-developer can also kick off a build and test the app.
So they can at least check whether the change does what they wanted it to do.
For this to be useful, the code doesn't even have to be good: think of it as a more accurate way to gather requirements and make a prototype. That's useful, even if you throw away the code.
GitHub's codespaces also drive home how the customer/user only needs a browser, which even people in legal will have. No additional software required on their end.
So they can at least check whether the change does what they wanted it to do.
For this to be useful, the code doesn't even have to be good: think of it as a more accurate way to gather requirements and make a prototype. That's useful, even if you throw away the code.