Of course not, but it highlights the risk of Appeal to Authority: one's expertise in a specific field does not make them experts in others, even ones adjacent to their own. For a more local example, I have a lot of experience writing Python. Someone outside the field might mistakenly think my opinions on, say, Java, are equally informed. They're not.
Of course not. That would make him an expert on developing oncology drugs, not on the ethics of drug safety and especially not on communicable disease control.
If chemotherapy meds had the incredibly low adverse reaction rates of common vaccines with the same typically high effectiveness, I bet his general opinions on the subject would be different. No, of course we shouldn't require school children to get preventative chemotherapy because the risk-reward ratio would be awful. And of course we should vaccinate them against polio because there's trivial risk in the prevention compared to the life-altering effects of the illness.
Also an expert on drug safety and how to get drugs approved because he would need to go through the FDA to get it approved for chemotherapy.
Dr. Soon-Shiong was responsible for developing oncology drugs. Does that give him enough authority for him to evaluate RFK Jr's stance on drug safety?
You haven't researched him at all, have you?