That would only be true if their tests work well. In my experience, IgG and IgM suck big time, and I wouldn’t trust results. Would love to see one of those randomized studies with qRT-PCR tests.
The problem with RT-PCR is that it only pick up viral RNA from a currently active infection, while IgG and IgM (antibody) tests will tell you if the person tested had been infected in the past.
Also, depending on how effective the detected antibodies are in fighting off the infection, we might get insight in to how much immunity people have and how long it lasts.
You’re making a massive assumption there - that the IgG and IgM tests tell you if the person has been infected in the past. To which my experience says: no, it doesn’t. Both false positive and negative rates are very high in comparison to people previously negative / positive with RT-PCR tests.
Also, depending on how effective the detected antibodies are in fighting off the infection, we might get insight in to how much immunity people have and how long it lasts.
RT-PCR will not tell you any of that.