Originally Posted by
wxguy
USA-NRT for onward international connections empties directly into the terminal and rescreening is not required.
That's a special transit for US originating pax, at NRT only.
I suspect (but can't say for certain) that HKG requires all connecting pax to clear transit security. It was required on SQ1 for the HKG transit when that routing was SFO-HKG-SIN.