All true, but the last point is of only limited applicability in the determination of a rule contravention unless the athlete is a minor or has some cognitive impairment. It goes to the sanction, where reckless disregard, negligence, or wilful blindness may (but mot must) be considered mitigating factors relative to intentional acts.
Bottom line: unless they have a legally-recognized incapacity, it is the athlete’s duty to take reasonable steps to ensure that no banned substances are introduced into their body. What is reasonable depends on many things, including the specific context. Is it reasonable to suspect that whole foods sourced from the normal stream of commerce would contain banned substances? No, therefore we have tainted food excuses, especially where a sample of the food can be obtained by a neutral third party...and we don’t expect athletes to not choose such whole foods to consume.
Is it reasonable to suspect that a solution that is claimed to have performance and/or recovery-enhancing qualities, introduced via IV, would contain banned substances? It depends. If administered by a real MD in a medical setting with full records, then likely not—but the scale slips from there, all the way to some private joker shoving a needle in your arm and connecting the other end to some plastic bag.
Yes, it happens—and YES, in most cases the athletes can be said to have had a duty to inquire and also to verify, with signed documentation. This is not kid’s stuff, for f’s sake—there could be anything in there, including toxins and pathogens.
It’s time for sprinters especially to start acting like adults, but I doubt that it will happen. It’s just not the culture. Yes there are individual exceptions to this, but the clowns will continue. They’re always trying to get one over, to stay one step ahead. They’re never just straight up, or rarely ever.
Until the penalties are increased to include things like restitution, the rewards will continue to be worth the risks, for many if not most sprinters. They typically have little to lose, and much to gain.
Bottom line, as in many other things: if it seems too good to be true, it probably is.