Grey goo doesn’t require intelligence of any sort tho just the ability to consume resources and replicate.

And it doesn’t even have to be nano machines, HzD is effectively a grey goo scenario with drones that can replicate and can produce essentially biodiesel.

Replication takes some kind of programming, perhaps not a statistical/machine learning type algorithm; but the example of a "navigation ai" also doesn't seem like it would be employing those techniques.