That’s not true at all; you can’t generally distinguish viral infections from bacterial infections by the length of illness. [charitably, this is somewhat a useful rule of thumb for many cold like illnesses, but the GP knew how long they were sick…and Covid is a good example of something some people are very sick from for a long time.]

Why do you think any real expertise is required for a situation like this? It’s a simple reality that medicine, like any field, is brimming with practitioners who do not follow best practices and even many that are not good at their job. Doctors make terrible decisions all the time. I can give you numerous anecdotes in my life where doctors were dangerously wrong even when presented with very clear evidence.