Not knowing the history here and I am too lazy to Wade through the numbers, I could see it being plausible that net, after taxes, the net increase may lag inflation because the floors of social security taxation at 50% and 85% are not indexed for inflation, where as all other forms of tax brackets are indexed for inflation.No, your Social Security COLA percentage is the same. The increasing taxation may change your net after tax dollar increase, but that's not the same thing as saying you get less of a COLA.
With minor variations, you've repeated this same complaint many, many times here. Everyone has had since 1983 (when I was 24 years old) to become accustomed to the fact that Social Security will be taxed (and since 1993 to understand that up to 85% can be taxed) depending on income. If you don't understand that now, you never will. And if you do understand it but don't like it, that's why you have representation in Congress; complain to them.
That’s not the same as saying the CPI adjustment is less. It is just bracket creep. Prior to the early 80’s income tax levels were not indexed for inflation and there was bracket creep even for income taxes. The tax cut bills in the early 80s eliminated tax bracket creep.