You're assuming all cancer diagnoses happen the same way.
All lung cancer diagnoses happen in roughly the same way.
Tumors are detected with CT scans, x-rays, and occasionally MRIs. To receive one of these scans, you have to schedule an appointment with a radiologist which can take several days.
Then, when they've confirmed you have a tumor, they do a biopsy to determine whether it is benign or malignant. For lung cancer, this is essentially a minor surgical procedure and needs to be scheduled with a specialist. This also takes several days, including the time you have to wait for a laboratory to evaluate your biopsy and determine whether you actually have cancer.
Absolutely none of these steps can happen within a single-day check up, and the process would ostensibly
begin at a routine physical, not end at one.
If you actually believe his story, you are handicapped.