See above? or as copied Retrospectively his condition may have been present for a number of years prior and wasn't/couldn't be detected. If all of the required/indicated investigations were negative and then guidelines stratified him into lower risk cohorts of diabetic, hypertensive elderly men he may not be (in the narrative he obviously isn't') above the level where his Class 1 is revoked.
That said, it's a narrative story with none of the references to the decision makers reasoning or guidelines/evidence applied to underpin the decision. His changing licence restrictions aren't annotated as he aged into the 60+ zone nor are the frequency and types of tests he most definitely would have needed prior to then to support the decision i.e. ATPL loss, CPL loss or restrictions etc. In the absence of these, and a point where you are correct, is that his baseline risk, without investigation would have likely precluded his renewal.
It's a repetition of previous, "here's a "safe" apple!!!!!" "now apply it to my orange". "Here's a single related story, and I say CASA got it wrong!!!!" therefore "everything must be wrong!!!"
The percentages were not linked to anything, just that they were in a range where it is not negligible and it's not above odds- I don't think Clinton in this case (and I'm not spending a couple of hours trawling through neuro/radiology journals) has a clearly evidenced prospective risk percentage (for or against a renewal), hence the waiting period/non consideration (as I understand it) for 12 months. I don't think the CASA decision reasoning has ever been fully placed on here, only Clinton's interpretation/recall of it and my perspective on what the reasoning possibly was.