Isn't the question whether or not we can affect the odds here? If we can increase it to 75:25 at this plateau, then we also are also increasing the age longest lived of these people are predicted to live for immensely, and the last person of this example group of 1 million starting at age 105 you give would expect that last person to die not 10 years later (at 115) on average as with a 50:50 mortality, but around 48 years later, at 153. Every slight change in that mortality rate affects that long tail quite a bit, relatively speaking.

I for one believe that might have an immense effect on how people view their health and longevity. If people believe that taking care of themselves might give them many decades of additional life instead of a few years, that could lead to a wider shift.