I'm not sure this is true. The fact that there is an *ideal*, a philosophical conception of "the ultimate intelligence" that scientists can try and strive towards, doesn't mean necessarily that scientists or atheists believe that this ideal is realisable within a universe that contains entropy, or indeed by 4 dimensional beings with mammalian brains.

But if a scientist tried to create immortality, or become "godlike" then if they achieved it, they would then have proof of "god". Of "a" god. Because they would be the god. So that's not logically incoherent, because atheists tend to disbelieve in god because there is no god that they have ever seen proof of, and theists have been unable to prove god's existence. But an atheist that then was confronted with irrefutable proof of god, such as by becoming a god themselves, would then have supplied themselves with the proof they demanded of theists, and be consistent.

An atheist saying "I don't believe in god because no one has ever been able to prove to me that god exists, indeed the preponderance of evidence indicates that god doesn't exist, therefore I am an atheist" and then, when science or technology or artificial intelligence or whatever becomes "godlike" (if such a thing is possible) would then say "well under such and such definition of god, there is proof of such a being, human-created, and now I believe in THIS god but not the others that still have no evidence for existing". That makes perfect sense to me.