That's the main reason I don't use any apps. I don't think there is a real need to suspect the official UI. If one doesn't trust the instance admins, then they should rather migrate.
In case of an application running on a server, there is no reliable way to make sure that the source being shared is the source that is deployed. As I said, I don't think you have any ulterior motives. I'm only trying to raise awareness around a specific problem with Lemmy. Perhaps I should create a separate post about this in relevant communities, if it hasn't been done already.
The user will have the option to revoke access for your application.