Yes, as far as Terraform is concerned during evaluation, aliased providers are just as independent as entirely different providers, they have different configurations and run in different processes.
If it turns out that you can run the dependent portions of the config with the same provider instance, that would be the best solution, and splitting up the config would not be necessary in that case. In the long term we can work on speeding up the dependency resolution across providers to prevent this kind of performance trap.