Unless the schema is self-modifying. Then obviously the database schema definition is the only source of truth.
The overall topic in this subthread was whether or not declarative schema management is appropriate and safe for "real" applications, as compared to traditional migration (imperative) schema management, for popular relational database systems.
If you're referring to exclusively using stored procs to generate dynamic tables or something goofy like that, then sure -- in that case you can't use any external schema management at all, whether declarative or imperative. But that doesn't mean that declarative schema management isn't a safe or possible approach for everyone else.
I don't know about declarative vs imperative. I can see "versioned migrations" are "coming soon", so maybe that could work. Depending on what it will be.