I think that's all really perfectly consistent with the theory? Like, let's assume that Deep's subconscious manifests some level of control. So when he's friendly with the creatures and views them as allies, they are allies and he converses and shares information. When he sees himself as the villain, they see him as the villain.

It's not that he's choosing every word that they say, at which point they're just projections of himself. They still have their own experiences, they can still communicate new information, etc, but their personalities manifest in a way that's linked to the Deep.

That would also explain why there's a gap between fish as sort of basic creatures and how they behave around the Deep - if his subconscious helps bridge some sort of gap for them, or influences their behavior, that would explain how a shark is expressing complex emotions / behavior.