I don't think it makes sense to compare interactions between, on the one hand, different groups of primitive humans on Earth and, on the other hand, interactions between interstellar intelligences, which might be (and in my opinion probably would be) some kind of distributed AI which does not think or behave like a living organism, the product of biological evolution.

My guess is that an extraterrestrial intelligence investigating the Earth would be very stealthy, for two reasons: firstly because, like scientists, they want to observe life on Earth without disturbing it, and secondly because they will naturally suspect that other extraterrestrial intelligences are also lurking around the Earth and will also want to observe those, if possible, and will understand that they'll have a better chance of spotting those other extraterrestrial intelligences if those other extraterrestrial intelligences don't spot them first and take evasive action.

So my conclusion from all this is that it's quite plausible that multiple extraterrestrial intelligences are already lurking around the Earth, with their probes disguised as tiny insects, for example, and probably they are not all aware of each other's presence.

They may be observing you now!