The problem here is that intelligence is not some linear scale, even general intelligence. We human beings are insanely optimized for social intelligence in a way that is not easy for a machine to learn to replicate, especially without detection. It is possible for a general AI to be powerful enough to provide meaningful acceleration of molecular nanotechnology and medical science research whilst being utterly befuddled by social conventions and generally how humans think, simply because it was not programmed for social intelligence.

Agree.

I think that since many AI risk advocates have little or no experience in computer science and specifically AI research, they tend to anthropomorphize AI to some extent. They get that an AI could have goals different than human goals but they seem to think that it's intelligence would be more or less like human intelligence, only faster and with more memory. In particular they assume that an AI will easily develop a theory of mind and social intelligence from little human interaction.

But in my experience the AI-risk advocates claim that safe / controlled UFAI is an impossibility.

I think they used to claim that safe AGI was pretty much an impossibility unless they were the ones who built it, so gib monies plox!
Anyway, it seems that in recent times they have taken a somewhat less heavy handed approach.