Do you think it's a strike against these points to call them
unfalsifiable? They seem no more so than any claim of technological possibility, such as "nuclear fission is possible", "fission chain reactions are possible", "nuclear weapons are possible", "nuclear fusion is possible", "nuclear fusion can be made economical", etc. Unless a technology violates laws of physics it's very hard to prove through math or experiment that something
can't be done.
But the AI safety groups don't just assume these without any justification. The existence of the human brain itself is either a proof and very strong launching point for most of these. In 1930, maybe you could have convinced someone that a nuclear bomb is impossible or at least an unfalsifiable worry, because one had never yet been built, but your reasoning is like trying to cast doubt on the possibility of artificial digestion, when there are already billions of stomachs roaming the earth.
The idea that a computer can't possibly be made to accomplish whatever a brain can is losing plausibility with every passing day. And as for surpassing it: a human brain is powerful, but has so many surmountable limitations, like: requiring 20 years of education to get up to speed with existing experts; dying after 70-90 years; not being able to run copies of oneself in parallel; etc. We only need to imagine removing these limitations, and doing so violates no known scientific principles.
It's like having a 50-megaton warhead in your lab, and meanwhile the rocket scientists are gradually figuring out how to make rockets fly, and you're saying "yes this is a big bomb, but the idea that one of these could be more dangerous if mounted on a missile is an unfalsifiable assumption!"