Neil Ferguson's 60% herd immunity threshold appears inflated

No.11880941 ViewReplyOriginalReport
NYC seems to have reached herd immunity, yet the estimates of the percentage of NYC residents with antibodies is only 20-30%:
>https://www.cnbc.com/2020/06/30/roughly-25percent-of-new-york-city-has-probably-been-infected-with-coronavirus-dr-scott-gottlieb-says.html
Why isn't this bigger news?