In the end, it is deterministic, as you say. But it's also quite more involved than you imagine. It's a big pile of interceptors (and their proper ordering), bootstrap classes, autoconfiguration, component scans, layered property sources and some more. Lots of it is not immediately visible and you have to start to read Spring source code. And it gets worse if the project gets set up in a way that makes it hard to deal with. For example, not organizing packages by feature. Relying on component scans at the default package is also not exactly funny.

When developing a Spring project, you indeed start to quickly appreciate the introspection feature that advanced IDEs like IntelliJ IDEA provide. Inspecting the application container at runtime is also possible, but it's a clear sign that your app got waay too complicated and has to be refactored.