You never made it clear why you believe that this episode takes place into a different reality than that in A Matter of Perspective. What is so different here that makes you believe that Sela didn't exist previously?
I wasn't trying to say that everything after "Yesterday's Enterprise" takes place in a different reality. Quite the opposite. I was trying to say that it takes place in the SAME reality only altered due to time travel. Yesterday's Enterprise did not depict time travel as a means of travelling through different realities where the reality they originated from is unaltered. If that was the case, we nothing would have been different when the Enterprise C when through the rift. But when it did go through the rift, we literally see this same reality being altered. When the Enterprise C goes back, this reality gets altered back to what it was, but with something... different. That's Sela.