Dependency injection provides the same hermetic-testing capability, so that's not really an answer to OP's question. Effect-as-world-model is, in this specific way, just a special argument slot that only accepts dependency-injected functions.

What effects provide beyond DI is entirely in their ability to abort (resume zero times) or (in the case of multi-shot effects) resume multiple times. An effect that resumes exactly once is structurally the same as a dependency injected lambda.