I've flown a number of times ..never had more than a cursory look at the PCR/ART test...SG, US, UK, GER...the check in agents aren't doctors. They are just processing the papers just as Carrotjuice described.

SQ was not banned for poor checking of documents, they were banned because of a silly rule imposed by HK that has clearly achieved nothing. HK should have focused on vaccinating people not banning flights...but I digress.