But Kojima has already made the distinction between Big Boss and Venom by calling Venom Big Boss's phantom.You are just saying what everybody knows. You are missing the point.
The two look and sound identical. Everybody believes both of them to be Big Boss. The two are active at different times, with VS being active during TPP and MG1 and NS being inactive from GZ all the way up until MG2.
They are both Big Boss. It is not incorrect to say Big Boss established Outer Heaven. VS continued to use the moniker after the events of TPP.
So it is incorrect to say Big Boss established OH if it was Venom who did it.
I don't know, we will just have to wait and see what happens and see if Kojima clarifies it in the third ending?
Edit: The distinction is made in the timeline.