All these sound personal. And the first one was yet another proof of what TearofGrace was saying for years. If uruk isn't sexually depraved, he isn't an uruk.
It's very rare, I've only gotten it around three times if I recall correctly, but I think it only happens if two captains have had previous encounters with each other, sort of like a rivalry. And, obviously, most enemy captains don't last very long in the wild before being either unalived or recruited. Plus you need both to survive the encounter and face each other again in a different nemesis mission.
That would be incredible funny and awesome, if it is possible, to get a Ambush-ception. Then one Ork asks "Wait... Who are you even guys?" Then a another Orks Answers "I don't know. we just thought it would be funny to join a Ambush, we didn't even created" :D
