I think what matters in this case is how proactive and greedy the model is.

GPT models are extremely proactive and gredy. So when Fable mentions something that may affect some obscure component of the system, GPT will start digging the codebase, execute web searches, re-read AGENTS.md and hit fable on the head.

Fable never does that, it just reads the turns and acknowledges it read them. This also explains why GPT models tend to overengineer things and why they're amazing reviewers if you triage their findings.