That looks to me like an antigen test, not a PCR test. And they are done with blood samples. [edit] Never mind, the blood tests are for the covid antibodies. I've done a few of which, forgot which was which. But still, the same points apply. They are meant to be used with mucus, not with other things.
Those things could be because they reported past deaths in a day, or isolated incidents such as a nursing home getting infected and many people there dying (although probably not everyone would die in the same day, so probably this is not the case).
Some countries, including mine, would sometimes report in a day deaths that were previously unreported.