I agree with everything you said except for that it may never see great use for building production apps. I don't think that App Studio is sufficient for production apps on its own, but I do envision a future where AI-based engineers (e.g. future descendants of SWE-Agent[0]) would use something like App Studio as a basis for doing the production work that you outlined there, with some of their automated testing involving replicating the behaviour of the App Studio app as the black-box "legacy system".
[0] https://github.com/princeton-nlp/SWE-agent