This type of naive response really is bothersome!
Humans are probabilistic systems?! You might want to inform the world's top neuroscientists and philosophers to down tools. They were STILL trying to figure this out but you've already solved it! Well done.
I don't think it's a naive response. Perhaps it's obvious to you that human doctors can't produce an "exact correct solution", but quite a lot of people do expect this, and get frustrated when a doctor can't tell them exactly what's wrong with them or recommends a treatment that doesn't end up working.
There's nothing naive about it. Most doctors work off of statistics and probabilities stemming from population based studies. Literally the entire field of medicine is probabilistic and that's what angers people. Yes, 95% chance you're not suffering from something horrible but a lot of people would want to continue diagnostics to rule out that 5% that you now have cancer and the doctor sent you home with antibiotics thinking it's just some infection, or whatever.