Timing is also important. I can predict cancer with 100% success, because everyone will get cancer, unless they die of something else first.

False positive rates are extremely important in the medical system as it exists today, where most scans will come without a known baseline and doctors cannot prescribe "biweekly scans for the next 6 weeks to see what changes". If we can achieve the kind of imaging abundance they're imagining (which I don't know how to evaluate based on their short post), I think false positives become much less of an issue, at least in the context of cancer where malignancy is the only problem.