Quite true. Given two investments of different risk, the riskier will be priced to yield more. Nothing you say negates this very fundamental fact of investments.
Yes, the new bond (after inflation jumps) will yield more. You still lose on your old bond. If you were correct then you still prove my point. A regular treasury pays more than the inflation adjusted one and so my yield over Social Security is even higher.
And another thing, what's the risk in buying bonds that would give the unadjusted one a higher return?
And risk is real. If your retirement investment fails then what will you do? You will ask the taxpayers to bail you out. So it means that private/risky schemes are based on the taxpayer subsidy which will the real source of the gain for the winners.