What can a provider developer assume about provider configuration arguments derived from other resource attributes?

I’m creating a provider and its configuration depends on the output of a resource, thus making the attribute unknown at configure time (as expected). I was expecting a failure when creating a resource from this provider that uses the configuration (saved in the provider struct), however it didn’t: the attribute that was previously unknown was now known. Is this the expected behavior ? Does Terraform defer the application of resources and updates saved attributes ?
I need to know if I can rely on this behavior.

Thank you for your time.