You continue to ignore the fact that if 60% of the people were immune to a virus with an R0 of 2.5, there would be zero spread because we’d already be at the herd immunity threshold. (HIT = 1-1/R0 or 60%).
Further, even at 40% that doesn’t make sense. New Jersey has seen ~28.1% of their population infected. At 40%, they’d still be 8.1% past the herd immunity threshold, so we would see a constant decline in cases and deaths. But both have been steady in New Jersey, indicating a continued viral spread.
This whole concept of any widespread “T cell immunity” is entirely theoretical. Could it be real? Sure. To what extent? Nobody really has any idea, but it is objectively not “40-60%”. If anything, it might simply explain why ~40% of infected persons show no symptoms. If that’s the case, it’s buying us nothing new that we don’t already know about. There’s no data to help quantify anything beyond that at this point.
And your 10% immunity makes no sense when we see contained populations where only 25% test positive. Not get sick, test positive. Keep forecasting 2 million deaths but the statistics do nit bear that out.