Here is an interesting article that has some bearing on FIML practice: Monitoring the Mind: The Neurocognitive Correlates of Metamemory.
This sentence from the article caught my eye: “To ensure the efficacy of the metacognitive system, continuous feedback between monitoring and control mechanisms is required…”
Though FIML is a mental operation that is quite distinct from the purview of this article, we can say that FIML practice basically ensures “continuous feedback between monitoring and control mechanisms” because partners work together, giving each other continuous feedback while mutually monitoring each other for coherence and accuracy in speech (and thus also memory, thought, cognition, emotion, etc.).
The article is more about self-monitoring within a single brain, but FIML practice results in stronger self-monitoring and retrieval of information by using partners to check each others’ work.