That’s pretty accurate.
It is not that the data is intentionally closed off. It is just that in terms of priorities, it has been less important to expose the management data via an API (or something you can use in an app).
That said, the App Gallery app is pretty much exactly this — it has information about each of the user’s apps. Actually internally, it also has the information about whether it is deployed or not. It is implemented as an AppSheet app. The only difference is that we have an additional “native” data source that provides access to a special set of “tables”. In this case, a special native table that lists the apps of the user.
We could expose this but we’ve been somewhat wary of it because not too many people actually need to use it. But if you expose it, people will use it and it is more surface area to have bugs in and break people when we change things.
Long-winded answer to say – no, we don’t expose this right now.