Good point, that will be an aspect to the Diplomacy in this game that is just absent from the AI diplomacy. Though if we're trying to even somewhat RP being primitive, we'll have to moderate it somewhat. After all, even if we've just recently developed 'Cooperation', that primarily applies within the tribe, not to other tribes, IMHO. At this stage of social development, a tribe would probably view anyone from another tribe as 'barbarians' and no better than the Neanderthals.
As to sharing information, I'd mostly agree with you, except that the plan is for (most of us anyway) to release either video or screenshot & text logs of the first 10 turns very soon here. This will give everyone some basic idea of where those who are doing so have started, and other info as well, so there will be less room in this game for evasions and deceptions than in a standard one.