The most pessimistic answer, if you want me to put on my "doomer" hat, is that we have been overcounting asymptomatic PCR positives* as cases (not least by setting Ct threshold high) and undercounting undetected symptomatic cases. If they roughly canceled each other out we would have a really high IFR (basically the current CFR) and are nowhere near herd immunity.

*This implies they don't develop a robust antibody response and are vulnerable to reinfection later, thus becoming a true case.

China did one thing right, and that's to not count asymptomatic carriers as cases. Makes things simple - and politically convenient too!

This is just a thought exercise. The discrepancy you point out bothers me too.