Exactly the point. Those skills are not needed to successfully navigate the Earth, yet we have developed them. The rationale was general self improvement and more control over nature. So the general premise is to ensure better and higher survival. Which is a changing objective function.

No reason why a GAI wouldn't have a similar instinct or capabilities.

Author also misposes no free lunch theorem. It pertains to algorithms not computational ability, and we're entirely not sure if true intelligence is an immutable algorithm. (Human is not, because of genetics.) There is no real equivalent theorem for self modifying algorithms, (or changing objective functions) and if there were, it will run afoul of halting problem.

Three theorem also had at least one known hole where it does not apply to coevolutionary algorithms. (Such as part of Alpha Go to go for an easy example.)

While environment puts on a hard limit, the limit is extremely high, on the order of 2^300. The optimising does not have to go for the simplest algorithm to solve the problem. And we do not know enough about informational capacity of matter in quantum states to be honest.