Why didn't they create a parallel timeline like in the reboot?
When the Enterprise crew went back in time why didn't they cause there to be a new timeline created much the same way when Nero went back in time with old Spock in the reboot a new timeline was created?
And when the Enterprise crew "returned" to their 23rd century (if such a thing would even be possible) would they find a whole new bunch of people living "their" lives as Kirk, Spock, Bones, etc. but having different faces? How bizarre that would be?