You are misusing statistics here.

You are dividing confirmed covid deaths by estimated covid infections, and that's not really valid.

When researchers study those with natural immunity, they examine people who are confirmed to have had covid before, so the CFR is the right number to use.

BTW, In the US covid has a CFR of 2%. It is not an "overestimate." It's not even an estimate. It's just what the number is. Obviously that number changes depending on the time frame, and it is (thankfully) dropping.