Where have you gotten all that information, exactly? I've been around ever since the kickstarter launched and the only lore the game has ever had until now has been exactly the same one told in the trailer.
"In 2034, nuclear attacks have decimated the earth. The remaining population are infected by an unknown virus. [...]"
"The game takes place in the near future, where a third world war has left the earth in ruins, and an unknown virus transforms the surviving humans into blood thirsty zombies."
"[...] When the sun goes down, the lunar cycle speeds up and strengthens the zombies".
That's it. That's all there's to the lore. In other words, nothing that really defines what the zombies are. You say it makes them kind of immortal, but they take bleeding damage from knives.
I guess my point is that nothing that's been said about the lore hints at zombies being sentient or smart, and that many things (such as the current AI) seem more like building blocks towards bigger threats for future alphas, such as bandits.
Maybe after bandits get added and once the devs start defining their lore a bit more, zombies will be left with a more simple AI, while the really smart AI is left for bandits, or maybe the devs are planning to define their zombies as intelligent and sentient, like you say. However, there's really been nothing that could hint at the latter option, certainly not in the lore.